A novel method for fabrication of self-supporting microbridge based on a-si films with tilted support legs for bolometer is studied in this paper. Based on the research of diffractive characteristics when the light passing through the mask in proximity lithography, we found if the distance of mask and photoresist is suitable, the intensity distribution curve of Fraunhofer diffraction (far field diffraction) at the border of contacthole is suitable to fabricate microbridge with tilted legs. By use of the method, the constant change of photoresist thickness around the contacthole can be realized using the far field diffraction proximity lithography. Then transfer the outline of photoresist to the sacrificial layer by plasma etching. Thus the fabrication of microbridge with tilted support legs was carried out easily, and this method has the advantages of low cost, simple and feasible.