Abstract: The transferred arc direct current plasma cutting torch was chosen as the studied object.According to the assumption of partial thermodynamic equilibrium and the theory of magnetic fluid dynamics, a mathematic model was developed.The plasma heattransferring and fluid properties were numerically simulated based on this model.The effect, which is induced by the cathode configuration and taper, the length of inside shrink and the spray nozzle, on the cutting current and the plasma temperature was demonstrated. The arc current density distribution was calculated based on the built model.The velocity field and temperature field of five sorts of shape of cathode and two sorts of length of inside-shrink were studied. Conclusion is drawn that cathode which have langer cathode spot area can produce higher velocity and temperature of plasma, and a significant effect of increasing of cathode inside shrink on the compression of arc has been proved.