A 1.55 μm all-fiber coherent laser demo system for high accuracy velocity measurement is presented. A 1.55 μm fiber laser is used as the transmitter. A fiber optical circulator and a telescope are used as the optical antenna. All optical devices are connected by single mode fiber. The signal and local oscillator (LO) filed are well matched with this system. Fast Fourier transform (FFT) is used to derive the signal Doppler shift. The experimental results indicate that the demo system can measure the target velocity accurately, the relative error of velocity is less than 0.2%. Besides, the problem from LO power intensity noise is discussed. The low-speed Doppler signal detection ability is improved by two orders of magnitude as a result of LO power intensity noise suppressed by pumping current modulation.