Abstract: A similarity calculation method was applied to establish the mathematical model to select the best coach. The index vector was defined to assess the coaching ability of coacher. The improved method was given to reduce the impact caused by the factor of time. The variance analysis was used to assess the impact caused by the gender. Based on this analysis，the whitening approach was used to remove the impact caused by the gender. To apply cosine similarity to select the best coach， criteria collected based on experience should be transferred as vectors， then compared with the idealistic coach. Many experiment results demonstrated the validity of the proposed method.

Key words: cosine similarity, variance analysis, index, idealistic coach, whitening approach