Abstract: A three-dimensional transient turbulent model of plasma arc was established based on local thermodynamic equilibrium (LTE) to study the effects of arc current,argon flow rate and hydrogen flow rate on arc fluctuation inside the argonhydrogen plasma torch by using computational fluid dynamics software ANSYS CFX.The results show that when the arc current increased but less than 600 A,the arc column became shorter, the average arc voltage and the arc fluctuation decreased, but the fluctuation frequency increased.However,when the arc current increased to above 600 A,it had little influence on the arc fluctuation.The increase of argon flow rate or hydrogen flow rate led to the increase of the arc column,average arc voltage and voltage fluctuation,but decrease of the fluctuation frequency.Among three process parameters,hydrogen flow rate affected the arc fluctuation most,and the arc current did least.