Based on amino acid addition model, a set of hydrophobicity contributions of amino acids was obtained from the multivariate linear regression analysis of peptides’ octanol/water partition coefficients. Multivedate regression was performed on a training set of 219 peptides including dipeptides to pentapephdes which we compose 21 natural andno acids. The correlation coefficients for the whole set fitting are 0. 978 and 0- 974, for log P and log D respectively. In addition, a new test method -evolution test-for regression analysis was discussed. The result of evoluhon test for amino acid addition model shows the advantage of this new test method.