The work aims to investigate the effect of carbon contents on the transformation plasticity coefficient and accurately simulate the residual stress distribution of 18CrNiMo7-6 steel after carburizing and quenching process. The samples with different carbon contents (0.21%, 0.49%, 0.65%, 0.87%) were carburized thoroughly and the expansion tests under different stress levels were performed to determine the transformation plasticity coefficient K of the samples with different carbon contents. The K values were put into DEFORM-HT for residual stress simulation. Meanwhile, a carburizing and quenching test was performed on a 16.72 mm cylindrical sample to verify the accuracy of simulating residual stress. The value of the martensitic transformation kinetic parameters did not change obviously with the carbon content, and a method was provided for calculating the K value of the incomplete expansion curve of the high carbon content sample based on . The transformation plasticity coefficients of the samples with different carbon contents were 7.16×10–5 MPa–1, 5.45×10–5 MPa–1, 5.53×10–5 MPa–1 and 6.01×10–5 MPa–1, respectively. Residual stress simulations were carried out with K=0 MPa–1, K=7.16× 10–5 MPa–1, and the K values related to the carbon content measured by experiments. The simulation results of the transformation plasticity coefficients measured by experiments were consistent with the measured residual stresses, and the residual compressive stress increased from the surface to the core firstly and then decreased. There is a carbon gradient in the surface layer of carburized and quenched samples, and the leading mechanisms affecting the transformation plasticity coefficient are different under different carbon contents, which causes the transformation plasticity coefficient to firstly decrease and then increase with the increase of carbon content, and has a significant influence on the residual stress distribution of 18CrNiMo7-6 steel after carburizing and quenching.