Abstract: Dynamic Charpy impact test of the X100 pipeline steel with different final cooling temperature and testing temperature was conducted. The fracture morphology and microstructure were observed. The results showed that when the final cooling temperature is 400°C, the crack formation and propagation energy maintains at a high level, anti-crack ability is good, a few layer phenomenon occurs only at -60°C. When the final cooling temperature is 520°C, the crack formation and propagation energies are reduced with the decreasing of testing temperature, the anti-crack ability decrease too, and the layer phenomenon at impact fracture is aggravated gradually. The maximal shock load is increases linearly with the testing temperature decreases. The fine and uniform microstructure and the tiny separation phases at the grain boundaries and bainitic laths are favorable to the impact toughness.