The effect of KBr on the size, shape and microviscosity of CTAB micelles has been investigated by means of laser light scattering (LLS), 1H NMR measurements and fluorescence probe. The data obtained from the various techniques are quantitatively in agreement. The Rh of micelles in 0.01 mol.L-1 CTAB solution increases from 3.5 nm to 43 nm and Rg increases to 89 nm with addition of KBr salt. In this process, both the microviscosity and molecular weight of micelles Mw have noticeable increases, too. The rod-like micelles are formed at 0.1 mol.L-1 KBr and the worm-like micelles are formed at above 0.2 mol.L-1 KBr.