In designing the power system of shield tunneling machine, a good calculation model is needed to forecast the cutter head torque in different earth layers. A torque calculation model of the cutter head in a test shield tunneling machine was presented based on the analysis of the factors and elements of the cutter head torque of the earth-pressure-balance tunneling machine, and its simulation model was built by AMESim soft. The torque characteristics in different earth layers and its change with different open area ratios of the cutter head were experimentally studied on a simulation shield test-bed and also simulated in the simulation model. The experimental results accorded with the simulation results. The torque calculation model was proved to be correct, and then the model was improved by a coefficient. Simulation shows that the torque mainly consists of the friction torque of the former ,the back and the circle face of the cutter head, and the cut torque of the slot region, the agitate torque in the soil cabin, and they are nearly 99% of the total cutter head torque.