In this paper,a convertion scheme of subcarrier frequency modulation signal is proposed based on Fabry-Perot cavity laser diode(FP-LD),including an FP-LD and an electro-optic phase modulator(PM).First of all,the sinusoidal phase modulation optical signal is obtained by the tunable lasers,electro-optic phase modulator and microwave source,then the phase modulated optical signal is injected into the FP-LD,and the low frequency phase modulated signal is convered into the subcarrier frequency modulation signal based on injection-locking in the FP-LD.In the experiment,the optical signals with 2 GHz,3 GHz,4 GHz and 5 GHz modulation frequencies are injected into the FP-LD,appropriate to be 22 GHz,21 GHz,24 GHz and 25 GHz subcarrier FM signal,respectively.