In order to evaluate the radiation and its impacts on workers during mountaincrossing tunnel construction, a suit of evaluation methods applicable to the tunnel construction with New Austrian Tunneling Method (NATM) is recommended. The average individual radiation dose of tunnel workers per year is chosen as evaluating indicator, and the environmental factors including air radon concentration, environmental gamma radiation dose rate, dust concentration and radionuclides specific activity are tested. The abovementioned assessment method is applied to the radiation environment of Mogangling Tunnel under different working processes. The assessment results show that the average individual radiation dose of workers in Mogangling Tunnel construction per year ranges from 0.203 to 1.13 mSv; therefore, the impact of radiation environment on workers is relatively low. The assessment method in this study considers different irradiation time of tunnel workers in different processes as well as multifarious radiation sources, and the selection of radiation indicators meets the actual situation at the same time. The study results can provide guidance for construction safety and radiation control in tunnel construction at abnormal radiation area.