Abstract: The thermal expansion properties of steels with different chemical compositions were precisely measured at temperatures from 30 to 1150℃ with a NETZSCH DIL 402C dilatometer. The curves of thermal linear expansion and instant linear expansion coefficient versus temperature were plotted from measured data. Quantitative analysis and comparison results show that carbon content has different influences on the thermal linear expansion and instant linear expansion coefficient of steels in the three temperature ranges of low temperature, solid phase transformation and austenite phase. Thermal expansion caused by the heat effect, which is basically the same for different steels, is dominant in the whole temperature range. The shrinkage of samples caused by phase transformation, which decreases with increasing carbon content, accounts for about 16% of the total absolute amount of thermal expansion, leading to the different expansions for the three steels.