The unmanned underwater vehicle (UUV) is the key of intelligent underwater combat, but its autonomous behavior ability is not capable for underwater unmanned autonomous combat. A mixed modeling method of UUV combat actions based on finite state machine and behavior tree was proposed to design the action model frame and the combat action model for UUV attack tasks. The model takes the advantages of the finite state machine and the behavior tree to obtain uncoupled frame, reduced structure and good portability. It supports customized development of UUV combat actions, task list design and UUV intelligent combat.