The invention discloses a coherent detection laser radar small light source used for an intelligent vehicle and a preparation method thereof. The coherent detection laser radar small light source comprises a semiconductor laser diode of which the end surface is coated by an anti-reflection film and a high reflection film and a hybrid Fresnel lens diffraction grating optical element. The output light end surface of the laser diode and the rear surface of the hybrid Fresnel lens diffraction grating optical element form a resonant cavity. The laser diode emits coherent beams which are collimated into parallel light by the optical element to act as incident light and mode selection is performed on the incident light so that the diffracted light of the optical element and the incident light are enabled to be collinear and reverse in direction, all or partial diffracted light returns to the diode along the original path, the part of diffracted light returning to the laser diode is oscillated and amplified in the resonant cavity and the reflected light reflected by the optical element is directly outputted to be the output laser and the other part of the diffracted light is directly outputted to be the output laser. The coherent detection laser radar small light source can be used as the core optical device in a coherent laser radar system and batch production can be realized.