Hi Lei,
http://www.cisco.com/c/en/us/td/docs/ios-xml/ios/sec_conn_vpnav/configuration/15-mt/sec-vpn-availability-15-mt-book/sec-state-fail-ipsec.html#GUID-12B9F69D-EE16-4CB6-81DD-427E9A2AC014
- Stateful failover for IPsec is supported on the Cisco Integrated Services Routers Generation 2 (ISR G2), with or without the Internal Service Module (ISM).
The config examples in this doc are valid ones. I'd check before deploying for known bugs to avoid problems down the line.
M.