Numerical simulations on the thermal convection of a neutral fluid (without a magnetic field) in a rotating spherical shell have been carried out. The results indicate that sufficiently rapid rotation results in strong differential rotation, with a pronounced equatorial acceleration. The formation dynamics of convection columns aligned to the rotation axis is studied extensively. A new generation mechanism of differential rotation is then proposed which concludes that the fluid motion generates an equatorial acceleration by selectively exciting the cyclonic columns in the spherical shell.