This paper focuses on the foreign theoretical models of trendline life assessment methods.Based on the basic concepts of tolerance intervals,tolerance limits,tolerance interval and limit of normal population, the established theoretical model is derived.On this basis,the regression model is improved in order to increase the prediction accuracy.Considering the actual situation,the improved regression model is discussed,the rationality of using a linear regression model as a trendline life assessment method is proved.Finally,taking a certain primer as an example for calculation,the result shows that the storage life of the primer is approximately 22 years.