Based on the quantum disturbance theory,a half-analytic model was achieved that can be used in the calculation of the eigen function and eigen energy of the two-dimensional clectron gas in a AlGaN/GaN heterojunction.The theoretical analysis and calculation result of the model were given.The calculation result was compared with that of the difference method.The method in this paper is superior to the difference method when solving a large-scale problem because of its convergence and efficiency and is well fitted for the calculation of the quantum well problem in the AlGaN/GaN heterostructure.