Because conventional method for tunable grating fabrication has harsh process condition, complex fabrication process, high costs and long cycle, a novel PDMSbased approach for fabrication of a tunable grating is introduced in this paper .By an oxygen plasma method to produce a micron scale grating structure, and making .Use of plasma free time controllability and excellent elastic of PDMS (maximum tensile was 120%), the desired grating can be obtained .Then by stretching the film along the grating line, as the grating line elongating，the grating constant decreases, the grating′s spatial period could be continuously varied and can obtain a predetermined target period. Experimental results show that the production of a grating tunable range is up to 40%, and the tuning process to maintain the integrity of the metal grating and diffraction angle varies significantly, the theoretical values and experimental values are basically the same. The experiment verified this method for adjustable grating fabrication has advantages of low cost, short cycle, simple process and easy to control,so it can be widely used in microspectrometer, scanners,optical communications and other fields.