The smart grids under the traditional security system is facing the impact of key leakage, quantum attacks and other risks, and there is an urgent need for a more secure encryption system to ensure the secure communication, while quantum encryption can fundamentally resist the above attacks. In this paper, a quantum encryption system for smart grid is proposed, and two key distribution mechanisms, wired and wireless, are designed, and the performance of the two mechanisms is modelled and analysed and simulated respectively. The experimental data showed that the Quantum Bit Error Rate (QBER) of the wired key distribution was below 1.5% and Quantum Key Generation Rate (QKGR) reached more than 3 Mb/s when the transmission distance was less than 10 km, and the quantum encrypted calls were analysed as an example of the wireless key distribution. The relationship between key update frequency and key length under different key consumption rates was analysed in the case of wireless key distribution.