Auto-ignition temperature of the combustible material is an important parameter in the process of industrial production which characterizes the risk of the material, which is also the necessary of quantitative risk assessmerit. In this paper AITTA 551 auto-ignition point tester was used to test the auto-ignition points of different binary systems, which was made of organic combustible liquids used in industry widely. Then, 28 group tests were carried out, and experimental dates of 168 binary systems with different components and volume r;tios were gained. The different components and volume ratios of auto-ignition temperature was explored. Three AIT change rules of combustible binary liquid mixtures were carried out by summarizing and analyzing such as linear rule, broken line rule and three-section rule. The rules were interpreted and the causes of the different variation were analyzed.