A method for implementing a number portability (NP) service includes: by a local NP database, receiving a called user number from a switching device; determining an NP database storing NP data of the callee according to a preset correspondence between the called number and identifiers (IDs) of NP databases storing the NP data of the callee; and obtaining the NP data of the callee from the determined NP database and returning the obtained NP data to the switching device so that the switching device routes a call to the callee according to the returned NP data. In addition, a system for implementing an NP service is provided, including an NP database and a switching device. Two types of NP databases are also provided. With the present invention, each NP database only needs to store partial NP data, which lessens the load of each NP database in storing and updating NP data.