An all-optical passive synchronous laser with master-slave configuration is built, the output power of the master laser pulse is amplified and injected into the slave laser, and the pulse synchronization between 1029.9 nm pump light and 1585.5 nm signal light is realized by using the cross-phase modulation effect of the injected pulse in the slave laser. An acousto-optic modulator used for frequency selection together with a cascade fiber amplifier enhances the peak power of pump pulse. In addition, the optimization of fiber link length effectively controls the spectral width broadening effect of pump pulse. The two-color synchronized pulse is processed via nonlinear difference frequency in PPLN crystal. When the repetition rate is set as 100 kHz, a linearly polarized picosecond pulse is achieved with 3-dB spectral width of 0.77 nm, central wavelength of 2940 nm, the maximum single pulse energy of 1.8 μJ , and pump light conversion efficiency of 49.6%.