Abstract: Gamma dose rate of fission gas is calculated by MCNP method and compared with the data measured by plastic scintillation. The fission gas absorbed by active carbon in source vessel was produced by neutron irradiation of uranium in Xi’an Pulsed Reactor. The simulation model is composed of geometry and material of source and plastic scintillation detector as well as the gamma-ray energies and probabilities of ⁸⁵Kr^m, ⁸⁷Kr, ⁸⁸Kr, ¹³⁵Xe^m, ¹³⁵Xe, ¹³⁸Xe and ¹³⁸Cs whose activities were measured by an HPGe γ detector. The presented calculation shows agreement with experiments less than 6% which consequently confirms the reliability of the simulation for gamma dose rate of complicated radioactive gas.