Fixing imaging 3D laser radar based on half-sine to rectangle correlation method was presented.Fourier series were employed to analyze half-sine to rectangle correction process.Theoretical analysis shows that half-sine to rectangle correlation can suppress high frequency noise and increase alternative component of modulation at the same time.The new method can achieve larger laser output power,longer measuring range while without suffering accuracy decrease.100 square meters targets in a distant about 20~70 m were detected by equipment based on the new method.The experiment shows that laser radar based on new method get an accuracy about 0.3 meters in a distance about 60 meters.The experiment result verifies the theory result.