Abstract:Fixed-point Digital Signal Processing(DSP) is widely used in the engineering applications because of its characteristics like high speed, low consumption, low cost and being programmable. However, the data dynamic range of fixed-point DSP is extremely narrow, which will cause “data overflow” when calculating the complex modulus according to its definition. An optimized method based on the traditional approximate calculation of complex modulus is put forward and realized on the fixed-point DSP. It can greatly increase the accuracy of the calculation of complex modulus in the guarantee of no data overflow.