Quantum billiards has attracted much interest recent years. There are many works on the two-dimensional billiards (2D). Compare with the 2D billiards, the three-dimensional (3D) billiards approaches with the actual system better. Taking the cubic billiards as an example, using the closed orbit theory (COT), we find the classical open orbits and study the correspondence between the quantum spectra and the length of classical open orbits in the 3D billiard system. The peaks' locations of the quantum spectra match with the length of the classical open orbits very well. This will help us to analyze the transport property through an open billiards. By this method, the physical image is clear, the computation is easier and it can help us to understand the character of some chaotic systems better. This is another example showing that semiclassical method provides a bridge between quantum and classical mechanics.作者简介：林圣路.E-mail: sllin@sdnu.edu.cn.通讯作者