Abstract: For the passive homing missiles, a developed guidance law based on optical flow was proposed to impact a moving target with an impact angle constraint. In contrast to optical-flow based circle navigation guidance, it is more practical and precise. Meanwhile the improved one does not require the range information, which avoids the problem that the range information can not be measured directly by a passive homing seeker. Based on a measurement model using an optical sensor and optical flow calculation and inspired by the insect navigation, the optical flow was used in guidance and control for a passive homing missile. Employing the structure of biased proportional navigation, the bias term was redesigned to ensure the impact angle. The simulation results show that, a small miss distance and a desired impact angle are obtained when the new guidance law is used to impact a moving ground target, also this guidance law is much robust to measurement noise.