The concept of similarity, originated from studies in botany, but has been widely applied in plant and animal geology, biology, ecology and even sociology. Based on the two bivariate analysis formulas SI=C/(A+B-C) and SI=2C/(A+B), two expression equations , SIJab…n=\[(∑Hij)2/n+(∑Hijk)3/n+…+Hab…n\]/\[∑Si-∑Hij-2∑Hijk-…-(n-1)Hab…n\] and SISab…n=\[2(∑Hij)2/n+(3∑Hijk)3/n+…+nHab…n\]/ ∑Si were developed to describe the coefficient of similarity for multivariate data. These two equations were validated using population distribution data of the common Noctuidae species from seven animal geological areas in China. By using these two equations, the species similarity and the relationship distance in the whole system overall can be efficiently measured. We suggest how to appropriately use these two equations to enhance the significant standard to 0.5 in Spensen′s formula, so that a consistent result for the same set of data can be obtained from both formulas.