In order to solve the problems existing in the parameter estimation of three-parameter Weibull distribu-tion，an improved total least square (ITLS) method is proposed for parameter estimation，and a differential evolu-tion (DE) algorithm is adopted for parameter optimization． DE helps to accurately and rapidly find a global optimal solution of the objective function in the optimization process，and ITLS helps to obtain realistic and reasonable re-sults because it considers not only the independent but also the dependent variables during the regression analysis．At the same time，by taking the square sum of deviations as the constraint rule，ITLS helps to achieve the best curve fitting effect with higher authenticity． The proposed method is then used to establish a three-parameter Weibull distribution model of a machining center，and the results are compared and analyzed． Analytical results show that the proposed method effectively improves the accuracy and authenticity of the reliability model of machi-ning centers and thus provides an effective method for the reliability modeling of the complete appliance．