Abstract: This paper analyzes static characteristics of plasma arc with the derivation of plasma arc mathematical model according to the application of low-frequency(LF) pilot arc technology in the plasma cutting power supply,and integrates with the control requirements in low-frequency (LF) pilot arc,arc transferring and arc energy transferring,and proposes a novel composite control strategy. In order to meet the power's control requirements of rapidity and stability with the load of low-frequency(LF) pilot arc,the inner loop of this strategy builds up voltage loop composite control with feed-forward arc voltage and feedback arc voltage,and the current outer loop controls the energy of plasma arc,forming a control method of feed-forward composite control of double closed-loop. Simulations and experiments were given to verify that the mentioned control strategy not only improved system's stability and robustness,but also had excellent dynamic responsibility. The power had well non-liner resilience, meeting requirements for plasma cutting power supply.