Objective To study the dislocation defect of silicon wafer which was polished by ultrasonic atomization chemical mechanical polishing (CMP). Methods The chemical etching method and optics method were used to analyze the morphology, density, and distribution of the dislocation etch pits. Besides, the influence of atomization quantity on the morphology and density of dislocation was studied by single factor experiment. Then comparative experiments were conducted with traditional CMP under the same conditions. Results The average dislocation density of the polished silicon wafer was about 1. 2×104 / cm2 and the dislocation density in edge area was lower than other areas. Besides, the dislocation morphology and dislocation density of silicon wafer polished by ultrasonic atomization CMP were obviously better than those treated by traditional CMP under the same conditions while the polishing liquid consumption was about one tenth of traditional CMP. The dislocation etch pits distributed evenly and there were no serious flaws such as dislocation piles and so on. In addition to that, the dislocation defect could be effectively improved by increasing the quantity of atomization. Conclusion Ultrasonic atomization CMP removed the dislocation defect of silicon wafer more efficiently than traditional CMP.