To calculate the dose distributions of 6 MeV photon beam at variable depth in 3D water phantom the MCNP4C2 code was used, and the simulated dose profile was compared with that of the treatment planning computer system (TPS), and a good agreement was found between them. In conclusion, the MCNP4C2 code package presents a good tool adaptable to get dose distributions for the 6MeV photon beam and it can be considered as confirmed method for patient dose calculations.