For the targets of limited size,the method of FPGA (field programmable gate array) based information system is proposed for target identifying.The coupling scan of transmission and four branch receiver are used to solve all aspect detecting, target is identified through four branch information. In the design, range counter, orientation counter, dimension counter are realized. So the target is identified. Through simulating, experimental result shows the effectiveness.The method can automatically identify con- ditions of missile-target meeting, advance the anti-fog interference capability of laser fuse,and improve at- tacking efficiency. The method is adapted to the ai-to-air missile and anti-radialization missile.