Numerical calculation for the equivalent surface source of the thermal neutron duct of in-hospital neutron irradiator mark 1(IHNI-1) reactor is carried out using MCNP Monte Carlo code. Cold clean criticality of B core is searched. Neutron beam parameters at the exit of thermal neutron duct are calculated. Equivalent neutron and γ surface sources for BNCT are built using equivalent surface source model. And these sources are reliable to calculate absorbed dose distribution in equivalent model of head quickly.