The present invention provides a method for realizing a one-number multiple-terminal service, the method comprises the following steps: a calling terminal calls a called terminal in a first network; the first network triggers, when the called terminal is a one-number multiple-terminal service subscriber and the called number is a main number, the call service to an intelligent service platform; the intelligent service platform obtains, from the first network, a Temporary Local Directory Number (TLDN) of the called terminal corresponding to the main number, stores the TLDN and sends a service control indication to the first network; the first network routes the call to a Next Generation Network according to the service control indication from the platform; the next generation network triggers the call service to the platform; and the platform returns the TLDN of the called terminal corresponding to the main number and all other terminal numbers bound to the main number to the Next Generation Network to connect the called terminals. The present invention further provides a system for realizing a one-number multiple-terminal service. The method and system disclosed in the present invention realize the simultaneous ringing and ordinal ringing of multiple user terminals by using a mobile terminal number as a main number.