The invention relates to a method for determining a critical state parameter in data of a large scale triaxial test on coarse-grained soil under a high ambient pressure. The method for determining the critical state parameter in data of the large scale triaxial test on the coarse-grained soil under the high ambient pressure comprises the following steps: firstly, placing the coarse-grained soil into a triaxial consolidation drainage shear testing device to be tested; secondly, obtaining data in the test; thirdly, calculating shearing stress in the consolidation drainage shear according to a formula (described in the specification). A component force parameter of a water pressure in axial direction of a test sample is increased, so that the negligence that influence of the water pressure is not considered in regulations in the prior art is overcome, and the formula in the method corrects an error that a shearing stress-axial stress strain curve (q-epsilona) is bent in advance under a high ambient pressure test working condition in a formula (14) in the regulation (SL-237-017-1999); according to the new formula in the method, test data automatically recorded by a computer is calculated, and consistency of critical state points (breaking points) obtained according to the shearing stress-axial stress strain curve (q-epsilona) and a volumetric strain-axial stress strain curve (epsilonv-epsilona) respectively is high, so that the method for determining the critical state parameter in data of the large scale triaxial test on the coarse-grained soil under the high ambient pressure is applicable to engineering application.