Abstract: There are many security threats in the Mobile Ofifce network. To ensure the data transfer security, Mobile VPN access scheme is usually used. The paper discusses a protocol conformance test method of IPSec VPN based on edge detection for smart phone. This method implements SoftAP with Hostapd, and captures packets between the connection of IPSec VPN by calling the libpcap library. It proposes a detection method based on session state of protocol, and tests the consistency of messages format between messages and standard speciifcation according to the transition of session state. The test results show that this method has considerable intelligence. It can analyse and recognize the non-standard protocol format of IPSec VPN packets, and what’s more, it is implemented simply and has a stable performance.