Synthetic aperture ladar is an advanced active optical imaging technology that overcomes the diffraction limit of the traditional optical system. This technology is inspired by the working principles of synthetic aperture radar in the microwave band. Compared with synthetic aperture radar, synthetic aperture ladar has several advantages such as fast imaging speed, high resolution, and its images being similar to what the eye is used to seeing, thanks to its operation wavelength, which makes synthetic aperture ladar potentially valuable. This paper aims to provide a comprehensive review of the progress made in key technologies related to synthetic aperture ladar, including its system model and basic theory, system design and structures, laser phase noise suppression technology, motion compensation technologies, and imaging algorithms. Furthermore, some important outdoor experiments at home and abroad were summarized. At last, the difficulties and challenges for the subsequent implementation of engineering were discussed.