A method for manufacturing a film support beam includes: providing a substrate having opposed first and second surfaces; coating a sacrificial layer on the first surface of the substrate, and patterning the sacrificial layer; depositing a dielectric film on the sacrificial layer to form a dielectric film layer, and depositing a metal film on the dielectric film layer to form a metal film layer; patterning the metal film layer, and dividing a patterned area of the metal film layer into a metal film pattern of a support beam portion and a metal film pattern of a non-support beam portion, wherein a width of the metal film pattern of the support beam portion is greater than a width of a final support beam pattern, and a width of the metal film pattern of the non-support beam portion is equal to a width of a width of a final non-support beam pattern at the moment; photoetching and etching on the metal film layer and the dielectric film layer to obtain the final support beam pattern, the final non-support beam pattern and a final dielectric film layer, wherein the final dielectric film layer serves as a support film of the final support beam pattern and the final non-support beam pattern; and removing the sacrificial layer.