Abstract: In order to solve the problems of low energy utilization and low efficiency in femtosecond laser micromachining, a new method of femtosecond parallel processing based on spatial light modulator (SLM) was proposed. Based on the discussion of the relationship between incident angle and diffraction angle, the principle of superposition of multiple diffraction gratings was analyzed. Multiple beams were generated by loading the phase holograms calculated using gerchberg and saxton(GS) algorithm on the SLM. The parallel femtosecond laser beam with the pulse width of 100 fs and the wavelength of 800 nm was focused inside a polymethyl methacrylate (PMMA) sample, uniform multipoint patterns of 一 and 工 were observed. Experimental results show that it is an effective method for controlling multibeam parallel processing.