Abstract: Two kinds of optical fiber sensors fabricated by fiber side polishing technique are proposed and demonstrated experimentally to measure the concentration of acetic acid. One of them is a side polished fiber Bragg grating sensor, whose cladding in the region of fiber Bragg grating is side polished. Because its reflective Bragg wavelength shifts when polished region is overlaid with different concentrations of acetic acid, the concentration of acetic acid could be measured.The other kind is a side polished single mode fiber sensor, whose part of cladding is side polished. The concentration of acetic acid could be measured by the transmitted optical power when polished region is overlaid with acetic acid. The resolution of side polished fiber Bragg grating sensor with a residual thickness of 0m is about 6.67%. The resolution of side polished single mode fiber sensor with a residual thickness of 0.5m is 0.55%.