Abstract: Sky-wave over-the-horizontal radar is the focus of development of over-the-horizontal radar as an effective early warning method in low altitude air defense system. By using optical cable communication methods, which have advantages of great information transmission capacity, rapid velocity, wide frequency band, strong anti-jamming capability, low circuitry loss and easy construction, modern sky-wave over-the-horizontal radar can achieve information transmission and system control of full coherent radar, which has excellent abilities of security, stabilization, antl-jammlng and anti-destruction.