The invention provides an optical self-focusing imaging device and method for synthetic aperture laser imaging radar. Focusing imaging is conducted on a radar echo signal through an optical imaging method. The optical self-focusing imaging device comprises a computer, a spatial light modulator and an image receiver. According to the core principle, a target echo signal received by a synthetic aperture laser imaging radar receiving system is stored in the computer, a quadratic term phase factor is added to the echo signal in the range direction through the computer and is then loaded to the spatial light modulator, light waves emitted by a laser are modulated through the spatial light modulator, focusing in the range direction and the azimuth direction is automatically and simultaneously achieved after a section of Fresnel diffraction is conducted on the modulated light waves, and the imaging result is received by the image receiver and is stored and displayed through the computer. The optical self-focusing imaging device is simple in structure, easy to integrate and capable of saving cost, and is an important technological improvement on the synthetic aperture laser imaging radar.