In this paper, Unsymmetrical Propellers are proposed in order to reduce the fluctuating pressure at blade frequency induced by a cavitating propeller. The idea behind the unsymmetrical spacing of blade is to give rise to a suitable phase lag between the fluctuating pressures transmitted from each individual blade. Pressure fluctuations can be roughly estimated in terms of the blade spacing by using Fourier expansions. In order to obtain the suitable blade spacing, an iterative calculation procedure is adopted. Finally five model propellers with non-uniform spacing of blades were designed. Experiments were performed with these five propellers and the one with uniform spacing. Comparing these results, the reduction of fluctuating pressure amplitude due to unsymmetrical propellers were verified.