Agricultural soil is a major source and sink of greenhouse gases (GHGs) including CH4, CO2 and N2O. In order to better understand the effects of plastic film mulching (F) on soil GHG concentrations, the concentrations of CH4, CO2 and N2O at 0-10, 10-20 and 20-30 cm soil depths in an annual hot pepper-radish rotation field were studied with the diffusion box method during a three-year period (2014-2017). Irrespective of mulching, CH4 concentrations significantly decreased while CO2 and N2O increased with the increase in the soil depth during both the hot pepper and radish seasons (P < 0.001). During the hot pepper season, F had not altered CH4 and N2O concentrations (P > 0.05), but significantly increased CO2 concentrations at 0-10, 10-20 and 20-30 cm soil depths by 1.59-22.55%, 4.27-18.16% and 8.20-23.63% (P < 0.01), respectively. In contrast, during the radish season, at 0-10, 10-20 and 20-30 cm soil depths, F significantly decreased CH4 concentrations by 2.70-10.00%, 1.43-14.88% and 0.47-29.30% (P < 0.01), but substantially increased CO2 concentrations by 18.83-38.73%, 22.53-47.88% and 3.36-30.98% (P < 0.001) and N2O concentrations by 3.37-57.54%, 22.60-57.71% and 44.25-63.16% (P < 0.05), respectively. Soil carbon and nitrogen were the main factors affecting CH4 concentrations while soil temperature, soil moisture, soil carbon and nitrogen were the main factors affecting the concentrations of CO2 and N2O.