Based on laser speed measurement, a method for high-accuracy speed measurement was developed by using femtosecond optical frequency comb based on the phase signal processing. The low speed measurement limit is μm/s level theoretically. The principle of phase changing was analyzed in detail, and a comprehensive model was established and simulated with MATLAB. The phase information of simulated measurement signals were processed by fast Fourier transform, and the speeds of μm/s, mm/s and m/s were measured respectively. Ideally, the measurement error was below 1 μm/s. In addition, arbitrary movement targets can be measured through the model. The movement state of target was restored with this method. The experiment was conducted to measure the speed of mm/s, and the relative errors were all within 4%. The results show that high-accuracy speed measurement can be achieved by using this method.