A new rigid-body refinement method for protein crystal structures is described. It is based on "Variable Metric Methods in Multidimensions" and "the Electron Density Map Correlation Coefficient". Test shows that the orientation and translation of the initial models can be improved effectively by this new method. And it can escape from the local extremum and reach the global optimum more easily than the maximum likelihood method when the search space has a large number of local extremum points.