The work aims to study the molecular structure and tribological properties of PA66 irradiated by gamma rays at different doses in atmospheric environment, so as to understand the change trend of tribological properties of PA66 under irradiation environment, and link the macroscopic changes of tribological properties with the microscopic changes at molecular scale, hoping to provide references for the application of PA66 in irradiation environment. PA66 was irradiated by gamma rays at doses of 50, 100, 250, 500 and 1 000 kGy in atmospheric environment, respectively. The changes of functional groups of PA66 were monitored by infrared spectroscopy and X-ray photoelectron spectroscopy, and the degree of molecular cross-linking and crystallization was evaluated by gel content test and differential scanning calorimetry. The tribological test was carried out by blocky PA66 and 6 mm diameter metal ball with reciprocating motion, and the friction coefficient during the test was obtained. Combined with the wear rate and wear morphology, the tribological properties and wear mechanism changes of PA66 before and after irradiation were analyzed. The results showed that the gel content of PA66 was 1.31% when untreated, and increased to 60.77% after gamma ray irradiation to 1 000 kGy, indicating that the molecular chains of PA66 were mainly cross-linked under γ-ray treatment. The results of infrared spectroscopy and X-ray photoelectron spectroscopy showed that the surface oxidation degree of PA66 increased with the increase of irradiation dose, and a new hydroxyl functional group was formed at 1 000 kGy. The crystals of PA66 were damaged by gamma ray. The degree of crystallization of the material obtained by DSC test was 30.78% under the unirradiated condition, and slightly decreased to 25.07% when the dose reached 1 000 kGy. The tribological properties of PA66 deteriorated significantly with the increase of irradiation dose, the friction coefficient increased from 0.49 to 0.615, and the depth and width of the wear tracks increased from 34.8 μm and 796 μm to 174.6 μm and 2 225 μm, respectively. When the radiation dose did not reach 500 kGy, the wear mechanism of the entire wear track was adhesion and plough cutting. When the radiation dose reached 500 kGy, the wear mechanisms of the center and edge of the PA66 wear track were significantly different. The material at the center of the wear track was still lost in the form of adhesion and plough cutting, the wear mechanism at the edge of wear track changed to fatigue wear because the new cracks were connected with the cracks generated by irradiation. Although the wear mechanism of the center of the wear track is the same before and after irradiation, the self-lubrication property of PA66 is weakened due to the change of the cross-linking degree of the material after irradiation, and the morphology of the center of the wear track is changed. The increase of single wear debris with the increase of radiation dose can support the deterioration of tribological properties of PA66 due to the increase of cross-linking degree.