A scheme for improving the long-term stability of a wideband tunable optoelectronic oscillator based on intermediate frequency phase-locked loop technique is proposed. In the scheme, an external tunable local oscillator is used to down-convert the RF signal of the optoelectronic oscillator to generate an intermediate frequency signal, which is independent of the oscillating frequency of the optoelectronic oscillator. Phase-locking of the intermediate frequency signal to a stable reference source can improve the long-term stability of the wideband tuanble optoelectronic oscillator. The impact of the phase-locked loop on the phase noise performance of the optoelectronic oscillator is also analyzed. Experimental results show that the frequency tuning range of the optoelectronic oscillator is 5~15 GHz, the phase noise is －121.2 dBc/Hz at 10 kHz offset and the long-term stability is 6.9×10－11/103 s. It indicates that the proposed method can significantly improve the long-term stability of a wideband tunable optoelectronic oscillator.