An automatic calibration scheme for the HBV model (ACSH) was developed. The ACSH was based on the physical significance of the model parmaeers and structure. The inference of hydrologists in the manual calibration was adopted as the guideline. A slight modeification of the model structure of the soil routine was suggested to avoid interdependence of the parameters. In total nine prameters, except the snow routine, Fc and MAXBAS, were calibrated automatically in two stages; first the soil moistute routine and then the others. There are six sets in two stages in total. Using the Powell method, the parameters im cach step were calibrated simultancously iwth carefully selected objective functions, and in particular a powerful objective function for the soil moisture routine. The steps were in a fixed order in the ACSH according to the model structure. The optimal values of the model parameters were stable, with the different initial values varying in considerable ranges. The optimal values of the model parameters were stable, with the different initial calibration when the ACSH was tested in two basins. The atuomatic calibration can thus be used as a reference or as an alternative solution of the model.