Generally, the self-supporting silicon nitride film structure is based on micro-nano fabrication technology. Fabrication of self-supporting silicon nitride film structure was studied in this paper, in which parameters of dry etching and anisotropic wet etching were optimized to enhance the quality of self-supporting film structure. Dry etching process included reaction gas ratio and etching time, anisotropic wet etching process involved etchant concentration and etching temperature. First, the experiments were conducted with different parameters. Then the surface morphology of the films fabricated in these experiments were observed by optical microscope, during which the ideal process condition was obtained by comparing the results. It was found that the addition of oxygen to the reaction gas can improve the effect of dry etching, and the best ratio of etching gas is V(SF6)∶V(CHF3)∶V(O2)=6∶37∶3, with 2 min etching time. In wet drying, etching with a mass fraction 25% etchant can achieve the maximum etching rate and ideal surface morphology of silicon nitride film.