In this paper, a high-efficiency silicon nitride (SiN) based air-clad type ring resonator that sandwiched with air cladding and SiO2 cladding for silicon photonic (SiPh) device was demonstrated. The simulation results showed that 400 nm-thick SiN waveguide have maximum coupling efficiency with a coupling loss of 7.2 dB. By using CMOS compatible process with single lithography (stepper) and reactive ion etching step, high qualities SiN waveguide was fabricated without silicon wafer warpage. The optical output characteristics of ring resonators with the free spectral range of 3.9 nm were obtained. This device can detect NaCl concentrations of 50-1000 mMole in deionized water. Therefore, SiN waveguide grating coupler is one of a promising SiPh devices for bio-sensing applications.