Wideband photonic microwave downconversion based on an optoelectronic oscillator (OEO) is proposed and demonstrated for the uncompressed HD video radio-over-fiber (RoF) transmission system. By using the injection locking of the OEO, high-quality RF carrier is extracted from the optical microwave signal. The extracted RF carrier is then fed back to the modulator to perform the downconversion in the optical domain. An experiment is performed. The distribution and downconversion of the signal with a carrier frequency of 10 GHz and a data rate of ≥2 Gb/s is verified. The wireless distance is 0.5 m and the length of optical fiber is 10 km. The distribution of a real-time 1.5-Gb/s uncompressed HD video is also demonstrated in the radio over fiber link. The results show that the system features wide bandwidth and low electromagnetic interference. Meanwhile, thanks to the automaic phase tracking of the OEO, no additional phase-locking operation is needed. The overall system is simple and stable, which provides a presentation and demonstration platform for HD video transmission.