The invention belongs to the technical field of laser application, and provides a horizontal Zeeman laser frequency locking method and device based on thermal frequency stabilization and acousto-optic frequency shift. By adopting the acousto-optic frequency shift technology, output laser frequencies of a plurality of horizontal Zeeman lasers based on thermal frequency stabilization are locked to the output laser frequency of the same reference horizontal Zeeman frequency stabilized laser, and therefore output laser rays of all lasers are uniform in frequency value. The purposes of overcoming the defect that traditional frequency stabilized lasers are poor in frequency uniformity and providing a novel laser light source for ultra-precise laser interferometry are achieved.