To satisfy the time and angle constraints of the unmanned aerial vehicle (UAV) in hitting target, a path planning method based on bi-arc trajectory is proposed. The initial and terminal velocity directions of UAV are classified, the corresponding analytical forms of bi-arc parameters and their monotonicity are derived respectively. Meanwhile, according to the analytic formula of bi-arc parameters, the unique degree of freedom for generating path is obtained, which reduces the input of path planning parameters. Then, the relationship between the length of bi-arc path and path parameters is analyzed, and a path planning scheme for multi-UAV cooperative attack is designed. The numerical simulation results demonstrate the effectiveness and practicability of the bi-arc path planning.