【Objective】 SCEM-UA algorithm was applied to optimal curve fitting method for hydrologic frequency curve and was compared with traditional methods in order to provide method support for hydrologic frequency analysis.【Method】 The optimal curve fitting method using SCEM-UA algorithm was adopted for hydrologic frequency analysis with the data of annual maximum flow during 1974 to 2003 at Yichang hydrologic station,and the sum of absolute deviation and the deviation sum of squares were calculated;the results wh...