Abstract: Coding excitation technique has been applied to medical ultrasonic imaging system. It is important that the transmitting codes and the corresponding pulse compression method must be chosen appropriately. In this paper the Tukey-windowed Chirp signal is adopted as a transmitting pulse, and the pulse compression method based on Fractional Fourier transform is proposed. Comparison of this method with traditional methods has been made.Simulation results show that the method of coding excitation based on Fractional Fourier transform is better than the traditional method in the aspect of needing less former information.