There is no uniform standard for determining the parameters of the key factors in the process of vacuum arc brazing. The parameters of the vacuum arc welding equipment are determined by the experience. Starting from the basic principle of arc,the influence of the key factors in the process of argon flow,breakdown voltage,breakdown distance and tantalum tube diameter is analyzed. According to the requirements of vacuum arc brazing process,the influence factors are obtained,which are most advantageous to the arc establishment ’s value range. Through the experimental data to verify and improve the theoretical research,in order to improve the success rate of vacuum arc welding equipment to provide a reliable basis for the value of the parameters and the solution.