A series of alkali-clearable azo disperse dyes containing a fluorosulfonyl group in their structures were synthesised. Various 4-fluorosulfonylanilines which were used as diazo components were prepared from N-acetylsulfanilyl chloride and coupled with corresponding coupling components to give 4-(N,N-diethylamino)-4'-fluorosulfonylazo benzene dyes. Depending on the various substituents present in the diazo component, absorption maxima varied from 469 to 620 nm in ethanol. The spectral properties of the synthesized dyes were examined with respect to the effects of substituents in absorption spectra, halochromism and solvatochromism. Thus, the appropriate Hammett substituent constants could be related to the observed absorption spectra and halochromism of the dyes prepared. In particular, the differences in dipole moments calculated by using computational method gave reliable predictions of solvatochromic effects.