This paper presents a target assignment and path planning framework for multi-USV defensive pursuit. The assignment is made by using Proportional Navigational guidance(PNG) law to precisely calculate the Predicted-Impact-Point(PIP). The paths to the targets are generated by dubins path and iterative Linear-Quadratic-Regulator(iLQR) method to avoid the collision. Simulations on combat situation with swarm USVs demonstrate that the assignment is made based on PIP, and the path is generated while detouring around the obstacle.