The graft polymerization in radio frequency hollow cathode plasma (RFHCP) is suitable for the surface modification of large-area thin film materials. The homogeneity of plasma surface modification of large-area thin film materials has always been paid close attention, and it is also the key factor affecting the industrialized applications of the technique. However, the homogeneity of plasma surface modification is thought to depend greatly on the distribution of discharge gas. In this paper, a finite element model is proposed to discuss the flow of discharge gas in hollow cathode plasma. The concentration distribution of the discharge gas has been discussed by the combination of numerical simulation of fluid distribution and pipe flow theory based on the investigation of the transport property of gas under vacuum. Comparisons between available experiments have also been performed to validate the applicability and practicability of the proposed model.