diff --git a/python/taichi/lang/kernel_impl.py b/python/taichi/lang/kernel_impl.py
index cad3a9f734c03..d4e21eb7b848a 100644
--- a/python/taichi/lang/kernel_impl.py
+++ b/python/taichi/lang/kernel_impl.py
@@ -1,9 +1,11 @@
 import ast
 import functools
 import inspect
+import operator
 import re
 import sys
 import textwrap
+import warnings
 import weakref
 
 import numpy as np
@@ -653,6 +655,11 @@ def func__(*args):
                     # so that it only holds "real" array shapes.
                     is_soa = needed.layout == Layout.SOA
                     array_shape = v.shape
+                    if functools.reduce(operator.mul, array_shape,
+                                        1) > np.iinfo(np.int32).max:
+                        warnings.warn(
+                            "Ndarray index might be out of int32 boundary but int64 indexing is not supported yet."
+                        )
                     if needed.dtype is None or id(
                             needed.dtype) in primitive_types.type_ids:
                         element_dim = 0
diff --git a/taichi/program/ndarray.cpp b/taichi/program/ndarray.cpp
index 4c9a6ab65c2f9..1a78cd4c2c467 100644
--- a/taichi/program/ndarray.cpp
+++ b/taichi/program/ndarray.cpp
@@ -51,7 +51,14 @@ Ndarray::Ndarray(Program *prog,
     total_shape_.insert(total_shape_.begin(), element_shape.begin(),
                         element_shape.end());
   }
-
+  auto total_num_scalar =
+      std::accumulate(std::begin(total_shape_), std::end(total_shape_), 1LL,
+                      std::multiplies<>());
+  if (total_num_scalar > std::numeric_limits<int>::max()) {
+    TI_WARN(
+        "Ndarray index might be out of int32 boundary but int64 indexing is "
+        "not supported yet.");
+  }
   ndarray_alloc_ = prog->allocate_memory_ndarray(nelement_ * element_size_,
                                                  prog->result_buffer);
 }
@@ -84,6 +91,14 @@ Ndarray::Ndarray(DeviceAllocation &devalloc,
     total_shape_.insert(total_shape_.begin(), element_shape.begin(),
                         element_shape.end());
   }
+  auto total_num_scalar =
+      std::accumulate(std::begin(total_shape_), std::end(total_shape_), 1LL,
+                      std::multiplies<>());
+  if (total_num_scalar > std::numeric_limits<int>::max()) {
+    TI_WARN(
+        "Ndarray index might be out of int32 boundary but int64 indexing is "
+        "not supported yet.");
+  }
 }
 
 Ndarray::Ndarray(DeviceAllocation &devalloc,