Abstract: The calibration process of hydrological models has a significant impact on model simulations.This study summarizes and analyzes multi-site, multi-variable, and multi-objective calibration studies carried out using the Soil and Water Assessment Tool (SWAT) model.The results show that: ① the application of multi-site, multi-variable, and multi-objective will affect the calibration process of hydrological models.② During the multi-site calibration process, it is found that not all multi-site calibrations can significantly improve simulation performance.The scale of the basin, the internal condition of the basin, the setting of the station, and the calibration sequence all affect multi-site calibration.In general, multi-site calibration in complex large-scale watersheds with numerous tributaries and heterogeneity can effectively improve the simulation performance of the model and reduce simulation uncertainty.③ The combination of multi-station and multi-variable calibration in the calibration process can better simulate the hydrological process of a basin and produce more realistic and reasonable hydrological parameters.④ Different objective functions also affect the calibration results, due to differences in calculation methods.Using multi-objective functions optimization, all information from the measured data can be comprehensively and effectively considered for better calibration.A hydrological model calibration optimization algorithm can be combined with multi-objective functions calibration to reduce the calibration time and improve the simulation effect.In hydrological simulation research, the number and location of multiple stations, calibration variables, objective functions, and calibration optimization algorithms should be selected with full consideration on actual situations of basins to obtain more accurate simulation results.