The secondary discharge is an important factor for power loss in the high-voltag e and high- power solar cell array. This paper studies the characteristics of th e secondary discharge and the breakdown mechanism through identifying the voltag e threshold where the secondary discharge will probably occur and monitoring the pulse current of the secondary discharge. The results show that increasing the operation voltage and string current will increase the possibility of the occurr ence of the secondary discharge on the solar array. The special structure design and the presence of RTV grouting between the solar cell strings can prevent th e secondary discharge incidents efficiently.