Optical tweezers,as a powerful tool of manipulation of micro-objects,is commonly used for trapping micro-objects and controlling their movement. Making use of the highly focused heat energy at the laser focus and the transportation ability of the optical tweezers,the process of crystallization,the shape of crystal separating out from solution,and the arrangement mode of the deposition from precipitation reaction can be controlled precisely,which may be used as a means of making micro devices. The laser-induced crystallization method and the laser-assisted precipitation method are used to make micro devices with the copper sulfate and the calcium carbonate as the based materials,respectively. Different factors influencing grow speed of crystals are investigated. The condition of precipitation reaction fitting to the laser-assisted precipitation method is discussed. By comparing,the method of laser-induced crystallization works more efficiently,while the method of laser-assisted precipitation can produce more stable devices. The experimental equipment and the proposed methods not only spread the application domain of optical tweezers but also provide a new way for fabrication of micro devices.