Abstract: Reliability design of mechanical components mostly focused on establishing pure theoretical mathematical model at present, without involving measured information for working components and gradual characteristics of parameters into theoretical model, which caused some errors for reliability design of components. In order to access reliability of existing components correctly, by taking strength of components as a process of independent increments, autocorrelation coefficient of strength was calculated, and effect of loading action and gradual change characteristics of strength was studied, thus a method for computing gradual change reliability was proposed. Combining the reliability design theory with sensitivity analysis method, a numerical method for gradual change reliability sensitivity design of components based on measured information was proposed, and the variation rules of reliability sensitivity of parameters at any moment and effects of design parameters on reliability of components were obtained, which provides the theoretical basis for structural design and life prediction of mechanical components.