An inclinometer based on dual tapered fiber is introduced. Corning single-mode fiber SMF-28 is used in the inclinometer. Two fiber tapers are fabricated in the fiber. When a light beam transmits through the first taper, high-order cladding modes are partially excited from the core mode. The cladding modes and the core mode propagate along the fiber together. When the light beam transmits through the second taper, the cladding modes are coupled into the core again and interfered with the core mode. As the effective refractive indexes of the core mode and the cladding modes are different, phase differences are introduced. The interference spectral intensity shows peaks and valleys at different wavelengths. As the effective refractive index of the cladding mode changes with the various of the tilt angle, the peaks and valleys of the interference spectral intensity will also shift. As a result, the tilt angle could be computed through the shift of a peak or a valley. Experimental results show that the tilt angle can be measured effectively with the fabricated fiber inclinometer. The accuracies for two directions are 0.151 nm/° and 0.087 nm/° respectively.