Abstract: The temporal and spatial variation of branch points was computed by four-dimension code of laser propagating in atmosphere. The branch points originating and annihilating were emulated. The evolvement of branch points in some propagating range with time was emulated, too. The computational results indicate that branch points are moving along with the movement of a light wave in the space, and they originate and annihilate in pairs. The position of branch points of distorted optical field varies with time when the propagating range is fixed. When the condition of laser beam propagating in atmosphere is fixed, the ensemble average of branch points of distorted optical field can be definite at the fixed propagating range.