diff --git a/setup.py b/setup.py
index e2a4b77f..c30a1078 100644
--- a/setup.py
+++ b/setup.py
@@ -22,6 +22,7 @@
 # SOFTWARE.
 #
 
+import atexit
 import os
 import subprocess
 import sys
@@ -34,6 +35,37 @@
 ENABLE_SPARSE = os.getenv("ENABLE_SPARSE")
 
 
+_warning_printed = False
+
+
+def print_platform_warning():
+    global _warning_printed
+    if not PLATFORM and not _warning_printed:
+        _warning_printed = True
+        RED = "\033[91m"
+        YELLOW = "\033[93m"
+        BOLD = "\033[1m"
+        RESET = "\033[0m"
+
+        warning_msg = f"""
+{RED}{'=' * 80}
+{BOLD}⚠️  WARNING: PLATFORM environment variable is not set! ⚠️{RESET}
+{RED}{'=' * 80}{RESET}
+{YELLOW}Please set PLATFORM to one of: cuda, ascend, musa, maca{RESET}
+Example:
+  {BOLD}export PLATFORM=cuda{RESET}    # For CUDA platform
+{YELLOW}In CI scenarios only, you don't need to specify PLATFORM. If it's not a CI scenario, please uninstall and then reinstall with PLATFORM specified.{RESET}
+{RED}{'=' * 80}{RESET}
+"""
+        # Use write and flush to ensure output even without -v flag
+        sys.stderr.write(warning_msg)
+        sys.stderr.flush()
+
+
+if not PLATFORM:
+    atexit.register(print_platform_warning)
+
+
 def enable_sparse() -> bool:
     return ENABLE_SPARSE is not None and ENABLE_SPARSE.lower() == "true"