The electronic states of GaAs/Al_xGa_1-xAs superlattices are calculated by the quantum interference effect. Compared with the K-P method, it is found that the results of two methods are accordance with the increase of the barrier width. This indicates the new method is suitable for calculating the electronic states of superlattice with the wider barrier,and is easier to manipulate than the K-P method. In addition, the photocurrent spectrum of superlattice sample is analyzed by two methods. As a result, the data given by the new method is closer to the experimental results than that by the K-P method. This confirms that the electronic states caused by the quantum interference effect exist in superlattice, and the new method can be applied to design energy band structure of the infrared photodetector.