The degree of stability which describes intensity of feedback is introduced into the dynamic equations of optical bistability with delayed feedback. In addition to relative delay time, the degree of stability also affects the instability behaviors of the system, including threshold condition and oscillation modes of instability. The threshold condition of instability is (S≥2 for long delay and S≥1+π/2Q for short delay. The experiment by a hybrid OBD shows oscillation, bifurcation and chaos and verities theoretical analysis. The results show the close relation between Ikeda instability and stability in OBD. New basis to realize Ikeda instability in intrinsic OBD has been provided.