From the analysis of operating characteristics of an oil pump,the physical meanings of the principal components originating from partial least-squares regression(PLSR) analysis was explained,and an optimizing mathematical model of oil pump's operating characteristic was proposed.This mathematical model is converted from non-linear expression into internal linear expression,so it gains the advantage of less calculative parameter and more inclusive information.This conclusion could be proved by the analysis of the data acquired from oil pump's all-purpose performance test.