Optoelectronic oscillator (OEO) is a hot topic recently and the tunability is one of its important performances. The step of the tunable performance at present is about 125 MHz and the step is long, which can be defined as coarse tuning. An experiment is made to prove the OEO based on phase shifter which can be finely tuned. By changing the voltage of the phase shifter, the phase shift of the oscillation frequency in the ring cavity can be tuning. The time delay in the loop will be changed which will change the oscillation frequency. Because the amount of phase shift of the phase shifter can be fine-tunned by the voltage, we can achieve a fine tunability. In the experiment we use an electrical phase shifter whose maximum phase shift is 180° realizing a fine-tunning OEO with the step of 70 KHz from about 10.02 GHz to 10.025 GHz,the range of 5.5 MHz.