Reasonable optimal system design and parameter optimization are prerequisite to achieve the functions of holographic femtosecond laser processing system. Based on the analyses of the requirements of the optical parameters of the holographic processing system, this paper makes an intensive study of the two key parameters. The oblique way which is more energy efficiency to irradiate the spatial light modulator is used to calculate the limiting conditions of the follow-up optical path design. Using the spatial light modulator and 4-f system which contain two lenses according to the demands of optical transmission, the optimal optical parameter design by deriving from the optical theory is given, and furthermore, the aperture simulation of the optical system with Zemax software identifies the rationality of the scheme. Finally, a reasonable holographic processing system is set up, and seven focus microlens arrays and micro gear parallel processing are achieved, respectively. Studies show that this optical design program can efficiently achieve the process of holographic femtosecond laser processing.