The influence factors of underwater acoustic propagation are the foundation of underwater acoustic communication. In this paper, a realistic underwater acoustic channel is modeled in the South China Sea. Three kinds of typical sea surface models with curvilinear boundaries are selected for the investigation by the BELLHOP ray model. Under different restrictions, the characteristics of the channel model are analyzed contrastively by changing the curvilinear surface types, sending and receiving depths and seasonal sound speed profiles. The experimental results present that (1) different types of curvilinear surfaces have little effect on the reflection with canopies and multipath effect but affect the mean transmission loss within limited depths, (2) convergent traits of transmission loss are becoming stronger and the influence of the surface is becoming weaker with the increasing of sending and receiving depths, (3) surface models perform differently on multipath effect and transmission loss under the conditions of seasonal sound speed profiles.