Based on optical phase-locked loop technology， a Raman laser system including three lasers，reference， master and slave lasers， is studied. Among which， the reference laser was firstly frequency-locked by modulated transfer spectrum technology and then as a standard frequency； the master laser， which has a frequency difference of 1 GHz relative to the reference laser， was red detuned from excited stated to prevent direct interaction between lasers and atoms； the salve laser， having a frequency difference of 6.8 GHz relative to the master laser， was used to excite the transmission between the hyperfine energy levels of ground state ⁸⁷Rb atoms. Respectively， the master and slave lasers were locked by two sets of optical phase-locked loop. The measurement results reveal that the phase noises of the two sets of optical phase-locked loop are within the range of 100 Hz to 1 MHz and lower than -70 dBc/Hz and -65 dBc/Hz respectively， and accordingly， the influence of phase noise on atom interferometric gravity measurement is as low as 5.3×10^-7 per shot. The master and slave lasers are amplified by two separate taped-amplifiers to ensure that the master laser’s power is half to that of the slave laser； the composition， polarization unification， and frequency modulation of both the master and slave lasers are realized by the combination laser transmission in fiber and free space. As a result， the Raman laser with a total power of 180 mW is realized， and the maximum fluctuation of total power less than 5% is achieved in long-term power measurement depended not on any additional power stabilizer， satisfying the experimental requirement of atom interferometry measurement.