Abstract: Slow strain rate tensile tests at 20, 40, 60 ℃ were conducted on X52 pipeline steel in the pure natural gas （hydrogen-free） environment and natural gas + 20vol% hydrogen （hydrogen-blended） environment. The influence of the hydrogen-blended environment on the tensile properties and the fracture morphology of the steel was studied. The results show that the hydrogen weakened the tensile properties of X52 pipeline steel, manifested as a decrease in plasticity and an earlier occurrence of fracture. As the temperature increased, the diffusion rate of hydrogen was accelerated, the hydrogen embrittlement sensitivity increased, and the trend of plasticity decline became more pronounced. In the hydrogen-free environment, the fracture of X52 steel was dominated by a microvoid coalescence mechanism, exhibiting typical ductile feature characteristics. In the hydrogen-blended environment, the fracture mechanism was a mixed fracture of toughness and brittleness; the edge area was dominated by quasi-cleavage morphology, while the central area was still dominated by dimple morphology. With increasing temperature, the quasi-cleavage feature became more obvious and the degree of brittle fracture increased.