This paper described the system structure of China Mobile Multimedia Broadcasting(CMMB) ,and the experiment testing system and the testing data of the CMMB are researched in detail. Then according to this research ,we have defined the failure criterion for the system of CMMB. Finally, with the combination of the DVB-H system's failure criterion, it is concluded that what is the subjective failure criterion and objective failure criterion in CMMB system.