In this paper, we investigate the parallel video coding efficiency on PC cluster. Some important factors that affect the parallel coding efficiency are analyzed: network performance, coding algorithm complexity and parallel mechanism. On Gigabit Ethernet PC cluster, a common MPI-based H.264 parallel video coding mechanism was designed, and a large number of tests and in-depth analysis were performed. Also this paper gives practical data analysis report and advice on how to build high-efficiency parallel video coding system on PC cluster.