Abstract: The test of average coefficient of linear expansion is important in determining the thermal property of the materials. The general testing temperature range is specified in GB/T 1036-2008. But different temperature ranges would lead to different test results, thus the testing temperature range need to be changed usually in practical application. Four kinds of epoxy resins were chosen to test the average coefficient of linear expansion under different temperature condition. The results show that the average coefficient of linear expansion of epoxy resins obtained in higher temperature range was higher than that obtained in lower temperature range. Moreover, softening would happen to materials at a certain temperature, and influence the testing results of coefficient of linear expansion.