The periodic optical power distribution of the optical microfiber coupler is calculated by numerical simulation with beam propagation method. A kind of solution sensor using microfiber coupler (MFC) surrounded with sucrose solution is experimentally demonstrated, and the experimental results show that the sensitivity of the sensor is wavelength-dependent. Both theoretical and experimental results have shown that the solution sensor is sensitive to the surrounding refractive index. With surrounding sucrose solution refractive index ranging of 1.330–1.400RIU,the resonant wavelength shifting has good linear relationship with surrounding refractive index changes, and the response sensitivity reaches to 1901.34 nm/RIU.