Liquefying shale gas into LNG product near the gas well can be of more economic flexibility in response to the problems existing in the development of shale gas in China. The cost estimation of liquefaction for the shale gas from Wei 204# well in Weiyuan was taken as the calculation case. Based on the propane-precooled mixed refrigerant liquefaction process， chemical simulation software Hysys was employed as the simulator. Software Design-Expert and Matlab were also used to optimize the composition proportion of the mixed refrigerant with the minimum energy consumption of the mixed-refrigerant cycle as the objective function. Then the formula for cost estimation was concluded according to the composition proportion above. The merit of simplicity makes the formula convenient and practical for cost analysis of the shale gas liquefaction in field operation.