For pipelines served in cold regions, excellent fractureFracture toughness is required to ensure safety and reduce the probability of brittle fractureFracture. In order to further improve the fractureFracture propertyProperties of API X80M steelSteel, the effect of microstructureMicrostructure on low temperatureLow temperature fractureFracture propertyProperties was researched in this paper. It was found that as the starting cooling temperatureTemperature decreased from 800 to 720 °C, the proportion of various types of microstructureMicrostructure changed, especially the proportion of polygonal ferrite gradually went up from 11 to 19%, and the yield strengthStrength and tensile strengthStrength gradually decreased. And when the polygonal ferrite content was 19%, the DWTT shear area value under − 15 °C was the highest, reaching 85%, which represented low temperatureLow temperature fractureFracture propertyProperties was the best. This is mainly because the testing steelSteel possessed the highest proportion of large angle grain boundaries and the smallest effective grain sizeGrain size.