Abstract: The dose distribution in a equivalent model of head in the case of operation for boron neutron capture therapy was simulated with MCNP 4B code. In order to calculate the absorbed dose rate of healthy tissue and tumor cells in the head, it was simulated by a double-ellipsoid equivalent model of head loaded with a tumor. Three cases of deep tumor case, deeper tumor case and shallow tumor case were studied. The result indicates that the absorbed dose in some grids can not achieve the treat standard of 18 Gy with irradiation. While in the same grid, the tumor is shallower, the absorbed dose is bigger, and the curative effect is better.