Keep-alive method, system and device for rear-end server in load balancing system

The invention provides a keep-alive method, a system and a device for a rear-end server in a load balancing system. The keep-alive method for the rear-end server in the load balancing system comprises the steps that a load balancing device sends a synchronous (SYN) packet to the rear-end server, receives an acknowledged (ACK) packet fed back by the rear-end server and judges whether a socket corresponding to the ACK packet is a keep-alive socket according to the ACK packet, wherein if the socket is the keep-alive packet, the load balancing device sends a reset (RST) packet to the rear-end server and identifies that the rear-end server is under a keep-alive state. Under the condition that connection with a transmission control protocol (TCP) service of the rear-end server is not built, health examination on the rear-end server is achieved, the rear-end server is prevented from generating a plurality of chaining logs, and consumption of system resources is reduced. Meanwhile, the whole health examination process is achieved only on an inner nuclear layer, the TCP service of an upper layer is completely transparent, and original services are not influenced.