Abstract: Based on geometrical optics formulation,this paper deals with the problem of angle-of-arrival influence of reflected beam by a reflector,and derived the expression of angle-of-arrival variance.The expression shows that:(1)the variance σr2 of angle-of-arrival is equal to zero,when the back reflector is illuminated by the beam of collimated or focused or spherical light beam;(2)the variance σr2 of angle-of-arrival is twice time of the variance of the line of sight path propagating beam when the specular reflector is illuminated by collimated or spherical light beam.