When radar seeker tracks low altitude target, monopulse tracking indication angle error will be caused due to target specular multipath interference. To solve this problem, a difference and ratio model was established under specular multipath interference, a monopulse tracking indication angle error model was deduced, an indication angle analytical expression was derived when radar seeker worked in open-loop and closed-loop tracking mode. Simulation results show that, for open-loop tracking, when the relative phase difference is 180° between specular interference and real target, the indication angle error is maximum: For closed-loop tracking, indication angle error is associated with the distance between target and missile, target height, antenna gain, and reflection coefficient. The closer the distance between target and missile is, the greater the indication angle fluctuations.