With the large-scale construction of smart grid, smart grid terminals widely using wireless access technology to communicate to the power systems. For ensuring the communication security, pair-wise key pre-distribution scheme is widely used, however, which introduces the complexity of key management, and insufficient security problems. According to the smart grid terminals wireless communication features, proposes an intelligent grid wireless terminal online key management scheme, which is based on the t rank binary symmetric polynomial and fully homomorphic encryption algorithm. This scheme make the communication key could be established with a few parameters between the communicating parties, which reduces the complexity of key predistribution and the amount of calculation. Moreover, the whole process of the key generation is encrypted by fully homomorphic encryption algorithm, effectively enhances the security of the scheme.