Abstract: Aiming at the technical requirements for the quantitative test of the electromagnetic radiation susceptibility in reverberation chambers, the limitation of the existing testing methods was analyzed and the key problems were pointed out. Based on the statistical distribution rules of the electromagnetic field in reverberation chamber and the electromagnetic radiation effect mechanism, the relationship between the critical interference field intensity of the equipment under test (EUT) and the effective mean value of the electric field intensity in reverberation chamber, the interference probability of the EUT and the maximum value of the equivalent antenna directivity factor was established. Considering the effect types and the coupling efficiency of the equivalent antenna, the selection principle and the fitting formula of the directivity factor of the EUT equivalent antenna were presented in three aspects, the interference and damage effect for the spectrum-dependent equipment, the high intensity electromagnetic radiation effect for EUT and the disturbance effect for the measurement and control equipment. A test was arranged with the condition, 10%~60% interference probability of the EUT and the stirring position number 30~50 in the reverberation chamber. The test results show that the result error of the EUT critical interference field intensity between the reverberation chamber environment and the uniform field environment is about 3 dB. A military ultra-short wave communication radio was selected as EUT to test the out-band high intensity radiation shutdown-restart effects and the measurement control disturbance effects of the power module. The test results indicate that the rule of the electromagnetic radiation critical interference field intensity varies with the radiation frequency for EUT, it is the same between the reverberation chamber and the uniform field environment. The maximum test error value is 5 dB, which can satisfy the requirements of the engineering test.