本文在总结北京谱仪（ＢＥＳ）粒子鉴别方法的基础上，提出了相对似然法．这种方法能充分地综合利用ＢＥＳ给出的信息量，与用简单选择条件组合的方法相比，比较明显地提高了粒子鉴别效率，同时降低了误判率．利用这种方法进行τ物理方面的一些研究，取得了较好的效果． Based on the summary of the BES particle identification method, this paper presents the relative likelihood method. This method can make full use of the information given by BES. Compared with the method of combining simple selection conditions, the method obviously improves the particle identification efficiency and reduces the false positive rate. Using this method to do some research on the physical aspects of τ, and achieved good results.