This article synthesized two carbazole pyridine N-oxide internal salts, 4- (9H carbazole 9-yl) pyridine 1-oxide (CPNO) and 4-(4-(9H carbazole 9-yl) phenyl) pyridine 1-oxide (CPPNO). It measured their UV visible absorption and fluorescence spectra in different solvents, showing good sensitivity to solvent polarity. The calculation shows that both compounds have a sizeable excited state dipole moment, which is the reason for the solvent polarity sensitivity of the compound. The research results provide a new approach for developing novel fluorescent polarity probes.