From the spatial structure of the grating, the amplitude distribution ［(θi)］ of not-even grating and the characteristic of light intensity ［I(θi)］ were deduced with the formula of Fresnel diffraction. The curve of I(θi)～θi was plotted by using the Maple procedure and the diffraction characteristics of not-even grating was obtained. The distribution of (θ) and I(θ) of the one-dimensional (D) transmission surface grating is correlated not only to grating constant but also to each single gap width. The result supplements the property of the flat surface grating differaction, and provides with theoratical basis to adjust,design, develop, and test the spatial structure of grating.