Abstract: Kripkes theory of necessity of identity has a significant impact on contemporary philosophy and logic.Kripke thinks that the philosophical interpretation of the identity statements is based on the metaphysical definition of necessity and ontological reflection,and that if the identity statements composed of proper names and the identity statements of scientific theory are true,they must be necessary.The deeper foundation of the argument for Kripkes theory of necessity of identity is based on the diametrically dichotomy between rigid designators and descriptions.Only by strictly distinguishing the logical functions of them can we forcefully reject the viewpoint of contingent identity and thus defend the necessity of identity.Kripkes theory of necessity of identity contributes to the development of its essentialism.Only the essence can stand the test of necessity,and is the only criterion for an individual to remain identical with himself.Explaining the necessity of Kripkes identity statements from the distinction between rigid designators and descriptions is helpful for a profound grasp of Kripkes theory of necessity of identity and for deepening the understanding of contemporary philosophy of language and metaphysical issues.

Key words: identity, necessity, rigid designators, descriptions, essentialism