A method of Secure User Plane Location includes: receiving, by a home SUPL Location Platform (H-SLP) of a target SUPL Enabled Terminal (target SET), a positioning request of the target SET from an SUPL Agent; positioning, by the H-SLP, the target SET and obtaining a position estimate of the target SET; sending, by the H-SLP, a location notification message carrying the position estimate of the target SET to a third party client based on information of the third party client obtained. Embodiments of the present invention also disclose an SUPL system including: an SUPL Agent, an H-SLP and a third party client. The technical solutions in accordance with the embodiments of the present invention meet the demand of informing the third party client of the position estimate of the target SET and further extend the application scope of the SUPL protocol.