It fails in the analysis of the structural parameters of the varied-line-space grating because of thespectrum aliasing phenomenon in the Fraunhofer diffiraction patterns. To overcome this problem, the experimental scheme relies on the prineiple of dilating window Fourier transform with loeal analysischaracteristics in stripe analysis and the Fraunhofer diflraetion principle , to theoretically derive and establislthe relationship between the characteristies of local varied-line-space grating diffraction pattern intensity!distribution and the corresponding structural parameters. For the designed optical system , a slit with tunablewidth is introdueed into the traditional Fraunhofer diffraction optical system as a window to obtain the loeavaried-line-space grating ,and to perform localization analysis, Finally ,a numerical analysis system is developer based on MATLAB to perform the numerical simulation and the optical experimental analysis by ourselvesAccording to the characteristics of the difiraction intensity distribution , the structural parameters of the locavaried-line-space grating can be obtained.There are three types of varied-line-space grating are employed for experimental analysis, The structural parameters of the local varied-line-space grating are achieved successfullyby the captured diflraction patterns. Furthermore , the comparison with the theoretical numerical simulationresults ,and the error show that the analysis results are reasonable and feasible.