Parameter determination is the prerequisite for the simulation of rainfall and runoff in a hydrological model. Model and parameter uncertainty should be considered during that procedure. This paper started with an introduction of the theory on the multi2objective complex evolution (MOCOM-UA) algorithm of excellent global and local optimization capability for dealing with the complex problem of hydrological model calibration. Based on the Xin’ anjiang model

different searching mechanisms between the multi-objective approach based method and genetic and simplex algorithm were respectively discussed by rainfall-runoff simulations for the Baohe watershed in the upper reaches of the Hanjiang River basin. With the application of the multi-objective genetic algorithm coupled with the simplex method as an optimal solution

the Pareto space of parameters and the prediction extent of the model were calculated and analyzed under four objective function conditions. The uncertainties of the model and its parameters were preliminarily investigated.