On the base of laser modulation concept,only two modes of laser modulation,pulse interval modulation(PIM)and pulse width modulation(PWM),which can be used in laser semiactive guidance,was pointed out by theory analyses.By analyzing and studying the characteristic of many laser codes at home and abroad,and a new encoding method combining PIM and PWM,and the embodiment of its realizing method was pat forward.It provided with the developing trend of laser encoding in the end.