This research demonstrates an optical force enabled NEMS actuator, whose travel range can be extended by as much as 20%. By taking advantage of the high quality factor of the cavity, the cavity optomechanics can not only change the travel range of the electrostatic capacitive actuator, but also provide an ultra-sensitive approach to detect the mechanical motion. This method gives a new approach to extend the actuation range of NEMS actuator and an ultra-sensitive way to detect the small actuator motion. There are several problems for traditional electrostatic mechanical actuators, for example, the breakdown of the electrostatic force, in which the actuator can only move small ratio of the designed gap. Even through several proposals are used to solve this problems, such as adding another capacitor or feedback control. The unwanted capacitance becomes a much bigger problem, because the capacitance is much larger than the natural capacitance. In this way, this method is quite ineffective. The optical gradient force which arises from the optical energy, on the other hand, plays an important role in the actuator at the nano scale. Therefore, the optical force can play an important role in the NEMS systems and have more good ways to manipulate. In this paper, we worked out a NEMS actuator enhanced by gradient optical force. More importantly, this system can provide a good method to detect small mechanical motion.