In this paper theoretical investigation of photonic crystal based force sensor is presented. Photonic crystal ring resonator design is optimized for the improvement of quality factor considering the fabrication feasibility. For the optimized configuration a high quality factor of 15500 is obtained and it is found that it remains constant over the desired force range. The minimum detectable force is found to be 9 nN for 0.1 nm wavelength resolution. A high sensitivity of 11 nm/μN is obtained in the studied force range.