A kind of new all-fiber coherent Dopple lidar made with a 1.55μm laser, a beam expander, circulator, and a signal sampling and signal processing system based on a SOPC chip. First , no the acousto-optic modulator was proposed to lock the frequence of the local oscillator light .The system obtains the fundamental frequency signal and the echo signal with larger mount of frequency shift by linearly modulating the driving current provided by the laser driving device to the photonic crystal laser,and obtain the difference frequency signal by mixing the fundamental frequency signal and the echo signal Then,the simulation results indicate that the more noise is added to the signal,the more errors will be obtained from the calculation.then, the lidar system was utilized to measure the velocity of atmosphere produced by a fixed fan.The results conform very closely to the reference ,whose absolute errors are less than 0.15m/s. The experient results validate the accuracy of the lidar system.