The invention provides an IPSEC (internet protocol security) VPN (virtual private network) device, an isolation method thereof and an isolation system thereof. The device comprises an inner end host, an outer end host and a non-network isolation card, the inner end host and the outer end host respectively maintain the same IP (internet protocol) mapping table, each table entry defines information such as a primary address, a destination address and IP mapping ID (identity), a data packet realizes network isolation by modes such as IP head stripping and recombination, IP mapping table search and filtering, private protocol capsulation and decapsulation and non-network isolation card transmission, an IPSEC VPN network data packet is encrypted and decrypted on an internal network host by the data packet, the device can resist malicious attack behaviors and transmission of viruses, Trojans and malicious plug-ins, security isolation in connection of an internal network and an external network is really achieved, higher-strength security protection for the internal network, the IPSEC VPN device and the network service data packet is realized, and the IPSEC VPN isolation device is high in security degree.