Abstract: By including the increment of transformation-induced plastic strain into the additive decomposition of the increment of total strain, the constitutive equations for thermal-mechano-metallurgic coupled analysis are founded.On the basis of these equations, Satoh test of 9Cr1Mo steel is simulated by using finite element method. The calculated results from thermal-mechano-metallurgical coupled simulation and thermo-elastoplastic simulation are compared and analyzed.It can be found that the evolution of stress and residual stress level calculated by two methods are both different.Due to ignoring the effect of phase transformation, the phenomenon of stress release that has been observed in experiments can not be predicted in the simulated result from thermo-elastoplastic calculation.To calculate stress state in welding accurately, thermo-mechano-metallurgical coupled analysis should be made, and the effect of phase transformation should be taken into account.