A physical and mathematical models are established to simulate a single droplet impact onto a thin horizontal liquid film by using coupled level set and volume of fluid (CLSVOF) method, which has advantages in acquisition of interface geometrical parameters and keeping mass conservation. The evolution after the droplet impact is obtained together with isopiestic and velocity field at different parameters including impact velocity, droplet diameter and liquid film thickness. Influences of Weber number (We), droplet size and film thickness on the crown diameter and crown height are acquired, and the results indicate that the crown diameter and height could be increased by increasing We or by reducing film thickness. Furthermore, bubble entrainment phenomenon when the droplet impinges the liquid film are captured successfully and discussed. It is found that increment of both impact We and droplet diameter could help the emerging of bubble rings.