Based on the advantage and shortcomings of the current main methods of measurement of laser beam quality,an improved method was put forward. Base on the characteristics of the method,a circuit was designed in which the analog signal was differentiating before it was converted to digital signal by A/D converter. By using the MATLAB to carry out the simulation analysis,the method is proved that it can accurately recover the complicated energy distribution,and the circuit is proved that it can improve the measurement accuracy effectively.