A laser radar optical path autocollimation method and collimator are disclosed that comprise reflector, laser, signal detecting element, receiving telescope and computer. It's characterized in that it includes mirror bracket, a fixed plate is mounted on the mirror bracket, a movable plate is mounted on the fixed plate, the fixed plate is connected with the movable plate via springs, the reflectoris located on the movable plate, two sets of slide blocks/micrometer mechanism and driven step motor are mounted in the mirror bracket, there are push-rods on the slide blocks which extend from the hole on top of the bracket and the fixed plate to the underside of the movable plate. The slide blocks and the push-rods are motivated upwards by the rotation of the driven step motor, the movable plate is adjusted to rotate along the X, Y axis, and the target position of the reflector is fixed at last with high accuracy. The application prospect: atmosphere scientific experiment measuring apparatus and measuring means can be used in various laser radar systems.