Abstract: A method to study the behavior of axially loaded large diameter piles according to insitu static load test of an instrumented pile and theoretical analysis is presented. Purpose of the test is to determine parameters of theoretical analysis model, so diameter of test piles can be smaller and tests can be carried out separately for soil layers in different depth if necessary. When static load test finished, the data are fitted step by step by theoretical analysis and model parameters are found simultaneously. By theoretical analysis and modified model parameters considering representativity of the test and scale effect, large diameter piles are analyzed to study bearing behavior of the piles. Satisfactory results have been gained using this method in research on axial bearing capacity of the large diameter piles of a cable stayed bridge on Songhuajiang River.