diff --git a/be/src/vec/olap/block_reader.cpp b/be/src/vec/olap/block_reader.cpp
index fef95303a3e982..ec6bb5cc92b5bc 100644
--- a/be/src/vec/olap/block_reader.cpp
+++ b/be/src/vec/olap/block_reader.cpp
@@ -209,8 +209,6 @@ Status BlockReader::_init_agg_state(const ReaderParams& read_params) {
 Status BlockReader::init(const ReaderParams& read_params) {
     RETURN_IF_ERROR(TabletReader::init(read_params));
 
-    _arena = std::make_unique<Arena>();
-
     int32_t return_column_size = read_params.origin_return_columns->size();
     _return_columns_loc.resize(read_params.return_columns.size());
     for (int i = 0; i < return_column_size; ++i) {
@@ -513,10 +511,6 @@ size_t BlockReader::_copy_agg_data() {
 }
 
 void BlockReader::_update_agg_value(MutableColumns& columns, int begin, int end, bool is_close) {
-    if (!_arena) [[unlikely]] {
-        return;
-    }
-
     for (int i = 0; i < _agg_columns_idx.size(); i++) {
         auto idx = _agg_columns_idx[i];
 
@@ -526,7 +520,7 @@ void BlockReader::_update_agg_value(MutableColumns& columns, int begin, int end,
 
         if (begin <= end) {
             function->add_batch_range(begin, end, place, const_cast<const IColumn**>(&column_ptr),
-                                      _arena.get(), _stored_has_null_tag[idx]);
+                                      &_arena, _stored_has_null_tag[idx]);
         }
 
         if (is_close) {
@@ -535,9 +529,8 @@ void BlockReader::_update_agg_value(MutableColumns& columns, int begin, int end,
             function->reset(place);
         }
     }
-
     if (is_close) {
-        _arena->clear();
+        _arena.clear();
     }
 }
 
diff --git a/be/src/vec/olap/block_reader.h b/be/src/vec/olap/block_reader.h
index b60a5bc237319b..6f9792929db72c 100644
--- a/be/src/vec/olap/block_reader.h
+++ b/be/src/vec/olap/block_reader.h
@@ -119,8 +119,7 @@ class BlockReader final : public TabletReader {
 
     bool _is_rowsets_overlapping = true;
 
-    // Use pointer to avoid allocing memory during construction
-    std::unique_ptr<Arena> _arena;
+    Arena _arena;
 };
 
 } // namespace vectorized
diff --git a/be/src/vec/olap/vertical_block_reader.cpp b/be/src/vec/olap/vertical_block_reader.cpp
index 61d24e79f77004..646af24b6b8493 100644
--- a/be/src/vec/olap/vertical_block_reader.cpp
+++ b/be/src/vec/olap/vertical_block_reader.cpp
@@ -223,7 +223,6 @@ Status VerticalBlockReader::init(const ReaderParams& read_params,
     }
     RETURN_IF_ERROR(TabletReader::init(read_params));
 
-    _arena = std::make_unique<Arena>();
     auto status = _init_collect_iter(read_params, sample_info);
     if (!status.ok()) [[unlikely]] {
         if (!config::is_cloud_mode()) {
@@ -314,9 +313,6 @@ void VerticalBlockReader::_update_agg_data(MutableColumns& columns) {
 
 void VerticalBlockReader::_update_agg_value(MutableColumns& columns, int begin, int end,
                                             bool is_close) {
-    if (!_arena) [[unlikely]] {
-        return;
-    }
     for (size_t idx = 0; idx < _return_columns.size(); ++idx) {
         AggregateFunctionPtr function = _agg_functions[idx];
         AggregateDataPtr place = _agg_places[idx];
@@ -324,7 +320,7 @@ void VerticalBlockReader::_update_agg_value(MutableColumns& columns, int begin,
 
         if (begin <= end) {
             function->add_batch_range(begin, end, place, const_cast<const IColumn**>(&column_ptr),
-                                      _arena.get(), _stored_has_null_tag[idx]);
+                                      &_arena, _stored_has_null_tag[idx]);
         }
 
         if (is_close) {
@@ -334,7 +330,7 @@ void VerticalBlockReader::_update_agg_value(MutableColumns& columns, int begin,
         }
     }
     if (is_close) {
-        _arena->clear();
+        _arena.clear();
     }
 }
 
diff --git a/be/src/vec/olap/vertical_block_reader.h b/be/src/vec/olap/vertical_block_reader.h
index e1e8cfa1239b72..2043db4b00a590 100644
--- a/be/src/vec/olap/vertical_block_reader.h
+++ b/be/src/vec/olap/vertical_block_reader.h
@@ -108,9 +108,7 @@ class VerticalBlockReader final : public TabletReader {
     // for agg mode
     std::vector<AggregateFunctionPtr> _agg_functions;
     std::vector<AggregateDataPtr> _agg_places;
-
-    // Use pointer to avoid memory allocation during construction
-    std::unique_ptr<Arena> _arena;
+    Arena _arena;
 
     std::vector<int> _normal_columns_idx;
     std::vector<int> _agg_columns_idx;