The invention discloses short message number portability realizing method and system, wherein the method comprises the steps of: receiving a short message sent to a called number generating number portability by a called SMSC (Short Message Service Center); sending the short message to an NPMSC (Number Portability Mobile Switching Center); and sending the short message to the called number by the NPMSC. By the invention, the NPMSC for independently managing number portability users is arranged in the traditional network, the uniform specific management of the number portability users can be realized, the reconstruction of the traditional network is greatly reduced, and the system realizing cost is effectively lowered.