Abstract: The main purpose of this paper is to present the work in analyzing free vibration and computing free vibration frequencies of the pedestrian GRP bridge with skew cable stays built in Chongqing Jiaotong Institute with analytical method and energy method. By both methods, the results were in a good approximation and had also been verified by field tests on the GRP bridge.The main frame of the bridge was a box structure made of GRP honeycomb sandwich plates. The local free vibration frequencies of top plates and loagitudenial webs of the box structure had also been calculated and the results were satisfactory.