In order to make the laser interferometer can be used more conveniently in practical environment due to the problems of the loss of interference fringes when the velocity changes quickly in VISAR system and the high cost of the complex structure of the system, AFVISAR system is simulated and analyzed, combining with the optimized improvement of the experimental platform, the dual-coupling improved AFVISAR system based on single-mode fiber in the wavelength of 1 550 nm is proposed. The coefficient R2 of the regression relationship between the measured value and the real one is close to 1 and the error of measured velocity is limited less than 1%. The theoretical analysis and the experimental results show that the improved system is characterized by small power, low insertion loss and low cost and it can be easily coupled by other optical fiber devices and be modified by the datumization of computers.