Synchronizatioln and synchronizatioln manifold are ofsignificance in nonlinear science and extensively investigated in the physical literature, but few rigorous mathematcal analysis has been carried out on this problem, In this paper a concept of synchronizor is established which is more suitable in characterizing synchronzation phenomena than synchronizatioln manifold, and the exstence of generalized synchronizor in unidirectionally coupled systems is puoved under someconditions.