A method for manufacturing an MEMS torsional electrostatic actuator comprises: providing a substrate, wherein the substrate comprises a first silicon layer, a buried oxide layer and a second silicon layer that are laminated sequentially; patterning the first silicon layer and exposing the buried oxide layer to form a rectangular upper electrode plate separated from a peripheral region, wherein the upper electrode plate and the peripheral region are connected by only using a cantilever beam, and forming, on the peripheral region, a recessed portion exposing the buried oxide layer; patterning the second silicon layer and exposing the buried oxide layer to form a back cavity, wherein the back cavity is located in a region of the second silicon layer corresponding to the upper electrode plate, covers 40% to 60% of the area of the region corresponding to the upper electrode plate, and is close to one end of the cantilever beam; exposing the second silicon layer, and suspending the upper electrode plate and the cantilever beam; and respectively forming an upper contact electrode and a lower contact electrode on the second silicon layer.