Abstract: In order to calculate flow rate under suspended curtain,in which the design of suspended curtain can be optimized,based on the principle of groundwater dynamics,the characteristics of flowingaround zone and non-flowing- around zone formed under the influence of suspended curtain was analyzed respectively;With Dupuit hypothesis and damming effect theory,on some theoretical derivation,the modified large-well-method(MLWM) to calculate discharge rate under the suspended curtain for phreatic and confined water was introduced systematically,considering the needs of practical application,whose approximation(AMLWM) was deduced.Then,in the case of phreatic aquifer,by systematical numerical tests,the law of weight coefficient of water level(WCWL)in MLWM versus suspended curtain depth into stratum was studied,and the accuracy of AMLWM was verified.At last,the optimum design of the suspended curtain was discussed,in which the optimum model and its solution was introduced,which was applied to some relative numerical case.