In this paper, for the study of static random access memory (SRAM), the online-test and offline-test are carried out on the total dose radiation damages. The differences between the two kinds of test methods and physical mechanisms are investigated. The results show that SRAM present multiple failure mode, the online-test only includes one fixed failure mode and the offline-test includes multiple failure mode. Due to the restrictions on signal integrity at test frequency, the online dynamic current test value is significantly less than offline test value. Since the existence of imprinting effect, the online-test static current is significantly less than offline-test value when the device-stored data are opposite to irradiation data. The parameters that cannot be detected online, may lapse prior to the data that could be detected online. The results are significantly important for studying the total dose radiation effect and the experimental evaluation of SRAM under radiation environment.