This research proposes a scheme of power information system based on quantum communication, aiming at improving the reliability and security of power service transmission. The new algorithm LD-WFQ (improved weighted fair queue) prioritizes the data packets that are about to timeout by estimating the expected time consumption of the data packets to be encrypted, so as to reduce the quantum encryption timeout rate of low priority services. The experimental results show that the LD-WFQ algorithm does not affect the performance of high priority services while reducing the ratio of overtime data packets, and shows good optimization effects under different key request rates. Compared with the traditional WFQ algorithm, the LD-WFQ algorithm has obvious advantages in meeting the requirements of power business encryption and improving the utilization rate of quantum keys, and has practical application significance.