In view of angle tracking error caused by low-altitude multipath effects, low-level multipath geometry of missile-target relative motion was analyzed, a model of mono-pulse radar seeker angle tracking error was established, the method of window function was proposed to reduce the different and the sum beam side lobes of antenna, frequency diversity was used to deal with reception signal, the relationship between angle tracking error, missile-target distance and grazing angle was simulated. The result shows that the missile flies to target with Brewster angle, using the low side lobe and frequency diversity to deal with seeker signal, can effectively reduce the impact of multipath effects on the angle tracking error. This analysis can provide reference and help for improving radar seeker angle tracking accuracy.