Novel polyphenylacetylene (P1) containing naphthalimides units in the side chain was designed and synthesized. The structure and properties of the polymer were characterized and evaluated by IR, NMR, UV, and PL. The measurements of sensing behavior to various halide anions, that is, F-, Cl-, Br-, and I-, reveal that the polymer is a ratiometric fluorescent chemosensors for fluoride ion. The polymer sensor shows spectral shifts and intensity changes in the presence of fluoride, in a wavelength-ratiometric and -colorimetric manner, which can detect fluoride concentrations in range of 10-100 mu M at visible wavelengths. The obvious colorless-to-yellow color change and blue-to-orange emission color change on the addition of fluoride ion are easily observed by naked eyes. It provides a feasible way to construct a ratiometric fluorescent chemosensors for fluoride ion. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 1544-1552, 2009