Radio-over-fiber technology has become an important solution for ultra wide band wireless communication, and the convergence of signal processing between optics and microwave/millimeter wave is more crucial. In this paper, microwave subcarrier phase modulation signal generation based on optical injection into a semiconductor Fabry-Perot laser is proposed. According to the period-one(P1) oscillation effect of laser output optical field, one modulation component of the optical phase modulation signal is amplified by sideband of P1 oscillation. The amplified component beats with injection optical carrier to generate microwave subcarrier. The phase shifts lead to the phase shift of subcarrier, thus the phase information is converted into phase information about microwave subcarrier. The optical phase-shift-keying signals at 1.3 Gb/s, 2.7 Gb/s, 2 Gb/s are converted into microwave subcarrier phase modulation signal, and the single sideband phase noise is measured. By logically comparing the demodulated signal with original signal, the feasibility of data information conversion is proved experimentally.