In the present paper, function test of different test pattern was used to investigate function failure of static random access memory (SRAM) induced by the total dose effect. By comparing the function test results of different test pattern and single error bit, it is shown that the failure mode of the device is data retention fault, and different storage cell had diverse data retention time, the fault module of device is the storage cell. We discussed the reason for these phenomena in detail using simple circuit model of storage cell, and also analyzed the influence of these phenomena on test method to evaluate the total dose radiation damage of SRAM.