Abstract: Description and statistical analysis to solder powder particle shape, which is made by ultrasonic atomization, have performed by using morphological methods since high angularity of solder powder particle and less regular shape which are key factors affecting the quality of solder paste preparation. Two important characteristics of solder powder particle shape, solder powder particle fractal dimension and aspect ratio, have been established. Firstly, the geometric projection image of solder powder particle was calculated, and then corrosion and expansion methods of morphology to characterize solder powder particle profiles were done. Moreover, the pattern information on the particle number and radius were statistically calculated. Finally fitting equation with fractal dimension was built. The experimental results showed that the morphological methods submitted by this article can be applied to segmentation adhesion welding particle image. In addition, the aspect ratio and fractal dimension of solder powder particle accurately reflect the solder powder particle real shape.