The application discloses a double host server system. A controller in the system comprises: an information obtaining module used for respectively obtaining the operation load information and data synchronous case of a main server and a standby server in real time; a server screening module used for selecting a server from the main server and the standby server as a target server according to the operation load information and data synchronous case; and an instruction transmit-receive module used for obtaining the operation instruction sent by a client, and sending the operation instruction to the target server for performing corresponding response processing on the operation instruction. According to the invention, before responding to the operation instruction of the client, the system first determines the target server according to the operation load information and data synchronous case, and utilizes the target server to respond to the operation instruction, thereby avoiding a lower progress processing speed caused by a higher server operation load, and ensuring a higher processing speed of the server system.