Improving design formula is an important way of increase design formula accuracy. The mean value and the coefficient of variation are the foundation of analysis formulas accuracy. Accuracy analysis and comparison of the same design formula applied in different ranges or different design formulas applied in the same or different ranges is an important part of evaluating design formula improvement effect. Establishing evaluation index and method of design formula improvement effect is an important basis in selecting and determining the design formula. Using strength-load interference model,reliability evaluation index and method were established that comparison single layer thick-walled cylinder burst strength design formulas improvement effect. In same or different ranges of application,the improvement effect of four burst strength design formulas for single layer thick-walled cylinder is analyzed and compared,the results can be reference for engineers in selecting and determining the design formula.