To prevent the override trip of mine electric power network, a scheme of preventing override trip system based on fiber-optic communication is proposed. The system depends on sending fiber block signals, and blocks superior line quick-break trip to achieve anti override trip. When the quick-break fault occurs, relays send blocking signals by using optical fiber to the upstream ones, and the time of quick-break protection will be changed automatically, to prevent the override trip. System test shows that, this scheme can effectively prevent the override trip and improve the operation of mine electric power network security and stability. And the correctness and effectiveness of the proposed scheme is proved.