In the galvo scanning laser drilling systems, the depth of processing is usually limited due to the short focal length. To solve this problem, a method based on high damage threshold spatial light modulator loading Fresnel lens phase is proposed. The focal length of the Fresnel lens is adjusted to change the position of the focus. As the machining depth increases, the focus position moves downward. Then the experiment processing and testing were carried out. The experimental results show that a high quality microhole with a diameter of about 330 microns was machined on stainless steel sample by using the method. The new method uses galvo scanning laser drilling systems and spatial light modulator to process microhole, which has a good application prospect in the field of laser processing.