A method is proposed for improving the stability of an Optoelectronic Oscillator (OEO) based on self-phase-locked technique. The output frequency stability of the OEO is improved by controlling an Optical Tunalble Delay Line (OTDL) according to the phase change of the OEO loop. The principle and noise transfer model are analyzed theoretically and verified experimentally. The experimental results show that the self-phase-locked OEO with a feedback control loop has a frequency drift within 0.9 ppm in 4 000 s, and its stability is greatly improved.