Microcantilever sensors have been known as a fundamental design used in force sensors, strain sensors and biochemical sensors. The fast-growing applications in nanoelectromechanical systems (NEMS) lead to strong demands in new sensing mechanism in order to downsize the sensing elements to nanometer scale. Photonic crystal (PC) based resonators have been investigated as promising solutions because the bandgap structure and resonator characteristics are extremely sensitive to the deformation and position shift of holes in PC resonators. In addition to the well-known nano-cavity resonator (NCR), we proposed hexagonal nano-ring resonators (NRR) of two different layout configurations. When a microcantilever under different force loads, both of the resonant wavelength and the resonant wavelength shift can be measured as a linear function of force load. The linear relationship between wavelength shifts and strain is observed as well. The minimum detectable force and detectable strain for NRR configuration 1 is derived as small as 0.0757 μN and 0.0023%. The outstanding sensing capability renders PC resonators as a promising nanomechanical sensing element to be integrated in various transducers for NEMS applications.