In this Letter, a highly sensitive and wide-range sensing system for fiber angular displacement measurement based on orbital angular momentum (OAM) beam interference is proposed and experimentally demonstrated. The system utilizes a micro polarization-maintaining fiber (PMF) as the angular displacement sensing element, effectively converting the angular displacement of fiber bending into an interference phase difference through the interaction of OAM modes and spherical wave interference. A dedicated algorithm is developed to demodulate the rotational characteristics of the interference image, enabling precise angular displacement measurement. Experimental results show that the system attains a sensitivity of 3524.158°/° within the range of 0°-2° and 53.849°/° within the range of 152°-2°. This system overcomes the inherent limitations of optical fiber angular displacement sensors, offering significant advantages such as improved integration, enhanced sensitivity, an extended measurement range, and robust resistance to polarization interference.