Abstract: The compression tests of ER70S-6 welding wire steel at strain rate of 0.01, 0.1, 1, 10 s^-1and deformation temperature of 1000, 1050, 1100, 1150 and 1200 ℃ were carried out by using Gleeble 3500 thermal simulation testing machine. It is found that increasing temperature and decreasing strain rate can reduce the flow stress in different degree. Based on Z parameter and linear fitting method, the constitutive equation of ER70S-6 steel was established by Arrhenius hyperbolic sine equation, and the activation energy Q is 313.821 kJ/mol. Finally, comparing the predicted and experimental values of the constitutive equation, the results show that the predicted values are in good agreement with the experimental values, the average relative error is about 4.52%, the linear correlation is 0.995, and the number of samples with relative error less than10% accounts for 95% of the total samples. The constitutive equation can be used to predict the deformation resistance of ER70S-6 welding wire steel and as a material model for finite element numerical simulation.