A process is proposed for crystallizing, by progressively cooling, in multiple stages arranged in series in a crystallization vessel (10), a descending continuous flow of a saturated sucrose solution at a temperature from about 78° to about 120° C., each stage maintaining the sucrose solution being crystallized at a predetermined temperature, until reaching a temperature from about 25 to 40° C., obtaining substantially pure sucrose crystals. A suspension containing sugar seeds is introduced in the crystallizing equipment, in the first stage, jointly with the saturated sucrose solution of 1.05-1.15. In another embodiment of the invention, the saturated solution is fed and its temperature is controlled, already in the first stage of the vessel (10), to obtain a supersaturation between 1.05 and 1.15, inducing the formation of small crystals used as crystallization seeds.