diff --git a/backend/app/__pycache__/alipay_provider.cpython-313.pyc b/backend/app/__pycache__/alipay_provider.cpython-313.pyc
index 9856ee0..cf66842 100644
Binary files a/backend/app/__pycache__/alipay_provider.cpython-313.pyc and b/backend/app/__pycache__/alipay_provider.cpython-313.pyc differ
diff --git a/backend/app/alipay_provider.py b/backend/app/alipay_provider.py
index b3fa2d8..4e4f23a 100644
--- a/backend/app/alipay_provider.py
+++ b/backend/app/alipay_provider.py
@@ -139,7 +139,11 @@ def _certificate_public_key(certificate) -> str:
         raise AlipayTransferError("支付宝证书必须包含 RSA 公钥")
     return key.public_bytes(
         encoding=serialization.Encoding.PEM,
-        format=serialization.PublicFormat.PKCS1,
+        # alipay-sdk-python's verify_with_rsa uses
+        # rsa.PublicKey.load_pkcs1_openssl_pem(), which expects an X.509
+        # SubjectPublicKeyInfo (BEGIN PUBLIC KEY), not PKCS#1's
+        # BEGIN RSA PUBLIC KEY structure.
+        format=serialization.PublicFormat.SubjectPublicKeyInfo,
     ).decode("ascii")
 
 
diff --git a/backend/tests/__pycache__/test_alipay_provider.cpython-313-pytest-9.1.1.pyc b/backend/tests/__pycache__/test_alipay_provider.cpython-313-pytest-9.1.1.pyc
index b6a2933..ce58eed 100644
Binary files a/backend/tests/__pycache__/test_alipay_provider.cpython-313-pytest-9.1.1.pyc and b/backend/tests/__pycache__/test_alipay_provider.cpython-313-pytest-9.1.1.pyc differ
diff --git a/backend/tests/test_alipay_provider.py b/backend/tests/test_alipay_provider.py
index 6aebb0a..e11e54b 100644
--- a/backend/tests/test_alipay_provider.py
+++ b/backend/tests/test_alipay_provider.py
@@ -230,6 +230,23 @@ def test_root_certificate_serial_ignores_non_rsa_certificates():
     assert alipay_provider._root_certificate_serial([sm2, rsa, ecc]) == expected
 
 
+def test_certificate_public_key_uses_sdk_compatible_subject_public_key_info():
+    from cryptography.hazmat.primitives.asymmetric import rsa as crypto_rsa
+    import rsa as sdk_rsa
+
+    private_key = crypto_rsa.generate_private_key(public_exponent=65537, key_size=2048)
+
+    class FakeCertificate:
+        def public_key(self):
+            return private_key.public_key()
+
+    public_key = alipay_provider._certificate_public_key(FakeCertificate())
+
+    assert public_key.startswith("-----BEGIN PUBLIC KEY-----")
+    parsed = sdk_rsa.PublicKey.load_pkcs1_openssl_pem(public_key)
+    assert parsed.n == private_key.public_key().public_numbers().n
+
+
 def test_certificate_bundle_keeps_valid_certificates_when_one_block_is_unsupported(monkeypatch, tmp_path):
     bundle = tmp_path / "alipayRootCert.crt"
     bundle.write_bytes(