According to the existing problems in the supervision of onsite operation in electrical power systems, an onsite operation monitoring and command system is designed. The onsite video is transmitted to command center via servicers by wireless networks. However, the realtime transmission of video can't be guaranteed due to the instability of wireless network bandwidth. The video transmission delay is long and the frames are lost seriously. In order to make the video transmission realtime and integrity, a video optimal transmission method considering the frame similarity is proposed in this paper. Firstly, on the basis of the characteristics of H.264 video coding mode, the frame similarity parameter is marked to distinguish the frame importance. The network bandwidth changes are then monitored in realtime and the PrioDrop scheduling algorithm is employed, so the important frames can be transmitted in advance. Finally, a test is included for verification. It is shown that the proposed optimal transmission method can improve the decoding quality of transmitted video, and achieve the requirements of realtime video transmission. It also provides a technical guidance to enhance the power supervision and strengthen the emergency command.