Effect of 100keV proton radiation on the structure and tensile properties of PTFE film was investigated. The change in structure before and after proton radiation was mainly evaluated by means of differential scanning calorimetry. The experimental results show that under radiation of 100keV protons for the fluence less than 7×1015 p/cm2, the DSC characteristics including the phase enthalpy of transformations at room temperature ΔH rt1 and ΔH rt2, the melting enthalpy ΔH m1 and ΔH m2, the crystallization exothermal enthalpy ΔH c, and Tg II were decreased, while the melting temperature was increased a little with the fluence increase. The change in crystallization enthalpy ΔH c indicated the increase of molecular weight of the PTFE film, but for 150keV when the fluence exceeded the fluence of 1016/cm2, the molecular weight decreased gradually. With increasing proton fluence, the thermal gravity loss was decreased, while the initial decomposition temperature increased, demonstrating that crosslinking of molecular chains occurred. With the increase of the proton fluence, for proton with energy less than 150keV, the tensile fracture strength increased at first, but when the fluence exceeded 1016/cm2, the tensile fracture strength showed a decreasing trend. While for the proton of 170keV, the tensile fracture strength σ f increased abruptly at the fluence of 2×1013/cm2, with the fluence increasing further, the tensile fracture strength σ f decreased gradually. The change of tensile properties could be related with the competition of branching crosslinking and the scission degradation.