Embodiments of the present invention disclose a method of implicit detachment and related system and device. The method comprises: the first device receives a request message that carries implicit detachment indication from the second device; and the first device performs implicit detachment or restores the second device to original status according to the indication. Embodiments herein further disclose a system and device for implicit detachment. In embodiments herein, implicit detachment process is triggered through MRT expiry information.