Abstract:This paper mainly deals with paleoenvironment of the Miocene diatomaceous earth of the Shanwang Basin. Diatomaceous samples were collected both horizontally and ventically from the Basin. The method of the fuzzy mathematics used, and a comprehensive study on the different diatom assemblages in sections (No. 1, No. 4, No. 5) show that in a graphic way the development and feature changes of the diatom assemblages of Melosira and Cymbella-Fragilaria. The changes in the scope of space and time indicate the water depth and the geographic area of the Basin. Another salient feature of the paper is the study of microstratum analysis on diatomaceous layers with different colors. Using the evidence of electronic scanning and information from δO18 method, the paper will probably give usefull information on seasonal temperature changes of the Basin.