A fringe-locking technique was employed to stabilize the optical parametric oscillator cavity, which would be affected by external environmental disturbance, such as vibration and airflow.First, how the locking point influence the squeezing degree was analyzed theoretically, the results show that position at half of the transmission peak could be the best locking point.Then the fringe-locking technique was applied to achieve the resonance between the optical parametric oscillator cavity and the injected infrared light experimentally.The experimental results show that the length variance of the cavity in continuous operation over 2 h is 7.27 nm and the longest locking time is 3.8 h, which is sufficient for the detection of the squeezed states of light.