This paper gives a brief description of the basic theory of settling simulation at home and abroad and studies the method for sedimentation to simulate a peripheral feed settling tank for municipal sewage treatment. The conclusion obtained from experiment shows that the flocculating suspended particles in the municipal sewage settle mainly in a state of gradient flocculation during the flocculation settling process. To simulate this gradient flpcculation settling, besides modeling according to the principles of equal-velocity flow and keeping similarity on water quality conditions, the ratio of influent suspended solids concentration must be made inversely proportional to the ratio of square root of settlion tank sizes, Co_m/Co_p=(lo_p/lo_m)~(1 2). According to this guiding idea, contrast tests in laboratory and in situ are carried out. Through observing the flow patters ia the models and comparing their hydraulic characteristic param eters and sedimentation efficiency with that of the hypotheical prototype, the equaton given above is verified with sufficient accuracy and practical value.