Abstract: In order to realize on-line laser shock hardening of components with fixed position and complex shape surface, the linkage method of laser peening system composed of four-axis robot and pulse laser was studied. By analyzing the communication mode, signal output and receiving mode between the robot and the laser, the requirement of signal receiving and sending which can be set up for equipment identification is analyzed, RS232 serial communication is proposed to realize the linkage of laser shot peening system. According to the signal requirement of four-axis robot for external communication, the corresponding signal conversion circuit, voltage drop circuit, single-chip square wave generating circuit and so on are designed. The relevant IO interface switch control program and RS232 serial asynchronous communication program are compiled, with hardware circuit and connection method developed, and the four-axis robot is realized. The signal interaction with the pulse laser achieves the satisfied effect of linkage.