A cladding-mode resonant specialty fiber sensor system is presented by using an intensity detection method. As a new type of fiber-optic sensor technology, the cladding-mode resonant fiber is sensitive to the measurands of the refractive index and bending. Based on the filtering transmission spectrum and narrow band distributed feedback laser, the variation of measurands can be transformed to intensity changes. In the proposed sensor system, a reference arm is added to reduce the affect of laser power fluctuation. The factors that affect the resolution are analyzed. This intensity-based all fiber demodulation technique has the advantages of low cost, simple configuration and requiring no mechanical adjustment. According to the experimental results of the refractive index sensor, a resolution of 0.0005 R.I.U. (refractive index unit) is achieved.