The load transfer mechanism of big-diameter rock-socketed pile was studied based on the rock-socketed pile static load test report of Mishui River Bridge, by conducting situ experiments. Based on the analysis of data from conducting situ experiments of the pile, the pile top load displacement curve was obtained, as well as the relationship of resistance size of rock surrounding the pile with displacement and the share ratio of pile side and end resistance, etc. The research results show that the friction resistance of pile body is influenced not only by limit friction resistance but also by normal stress.The value of limit side resistance provided by the prospecting report is smaller. The socketed section bears most of the pile top load, and the friction of socketed section plays the leading role, for the performance of the friction pile.In the process of loading, the proportion of the side of pile soil resistance decreaseds gradually, while socketed section total resistance increases gradually, and finally tends to be stable.