Abstract: Characteristics and mechanism of a droplet impacting on the liquid surface were studied experimentally. The process of droplet impinging on the liquid surface with different depths of the liquid pool was recorded with a high-speed camera, and the characteristic phenomena such as liquid crater, liquid crown, central jet and secondary droplet that appeared at different stages were summarized. An image processing program was developed and the automatic extraction of geometric parameters was then realized. The influence of pool depth Weber number, droplet diameter, and falling height on droplet impacts was discussed. The results show that: under the condition of constant Weber number, when the pool depth crosses a certain critical value, the characteristic phenomena such as liquid crater, liquid crown, central jet and secondary droplet change significantly; the ratio of the liquid crown height to the liquid crater depth increases within a certain range with the increase of Weber number; whether the secondary droplet can be separated by the central jet is closely related to the depth of the liquid pool and the diameter of the initial droplet.