In the design of existing guidance law for small missiles,the range of angle constrainsts is often limited.In order to expand the feasible range of angle constraints and achieve a full range of striking on the target,a guidance law which can achieve overhead attacking based on the principle of double arcs was designed.Firstly,the missile target relative motion model of terminal guidance phase was constructed,and the principle of double arcs curve fitting was proved and the key parameters were deduced.Finally,the guidance law was designed based on the principle,which can strike the target from any angle.The simulation results showed that the range of the feasible angle is greatly expanded,the guidance law even can lead to overhead attacking.Besides,the guidance scheme has a strong ability to control the impact angle,the overload near the hit point of the guidance law is much smaller than the biased PNG,the energy consumed is much less than BPNG,and the guidance scheme can satisfy the miss distance requirements.The significance of engineering is obvious.