The application of powder particle size measurement in engineering field are introduced, the major powder particle size research methods are also included. Furthermore we analyzed the characteristics of these methods. Based on these, we proposed a method, which makes full use of Matlab to process and analyze the SEM image of powders to get powder particle size and the distribution, and the method achieve a good effect. Finally, In order to verify the processing method, the authors performed an example of the approach. Based on the results, it can be confirmed, therefore, the method using MATLAB is convenient to analyze the powder particle size.