When the femtosecond laser is used in surface micro-structuring through a high NA objective lens, , too short of focal depth affects the processing performance. The focus discrete effects of the correction collar on the objective lens is analyzed. A method of holographic defocus control using spatial light modulator (SLM) is proposed. By varying the period of the annular blazed grating which is based on the diffractive axicon computer generated hologram (CGHs), defocus control is performed to form a long depth of focus. The distribution of focus axial intensity is expressed in the form of a row of micropores which are processed on the surface of polyimide film (PI), and the distribution is consistent with the simulation result. The defocusing process is performed using a 40× objective lens of 0.6 NA. When the center period of the annular blazed grating is 200 μm and increase progressively from inside to outside by 400 μm, a 50.90 μm uniform depth of focus can be obtained, which is 8.28 times the length of the depth of focus obtained by directly processing with high NA objective lens. In addition, the composite defocus process is performed by SLM and correction collar to further homogenize the entire region of depth of focus.