Disclosed is a method for determining the location of a targeted mobile set using SUPL (Secure User Plane Location) in a wireless communications network, including sending a target set location initiation message to the targeted mobile set in response to a request message, causing a home positioning server to exchange the capacities of positioning methods with the targeted mobile set to select and store a suitable positioning method, and determining the location of the targeted mobile set by using the selected positioning method previously stored whenever the location is requested. Accordingly it is unnecessary for the targeted set to resend the target set location initiation message to the positioning server whenever repeating the location calculation for the repeated deferred service.