A method for determining reachability of a terminal group, comprising: when a service network element needs to acquire the reachability of the terminal group, sending, by the service network element, a terminal group reachability notification request message to a Home Subscriber Server, wherein the terminal group reachability notification request message comprises information of the terminal group; and when the HSS determines that the terminal group is reachable, notifying, by the HSS, the service network element that the terminal group is reachable; wherein the operation that the HSS determines that the terminal group is reachable comprises: after the HSS receives the terminal group reachability notification request message, the HSS sets a terminal group reachability request parameter, GRRP, locally, and forwards the terminal group reachability notification request message to an MME; and after the MME receives the terminal group reachability notification request message from the HSS, when the MME locally detects, according to the information of the terminal group, that a Paging Proceed Flag of a representative terminal of the terminal group has not been cancelled, the MME determines that the terminal group is reachable, and the MME notifies the HSS that the terminal group is reachable; and after the HSS receives the notification that the terminal group is reachable, the HSS cancels the terminal GRRP locally; or when the MME detects that the PPF of the representative terminal of the terminal group has been cancelled, the MME sets the terminal GRRP locally, and after the MME locally detects an activity event of the representative terminal of the terminal group according to the information of the terminal group, the MME sends a terminal group activity notification message to the HSS and locally cancels the terminal GRRP; and after the HSS receives an update location message of the representative terminal of the terminal group or the terminal group activity notification message from the MME, the HSS determines that the terminal group is reachable, and the HSS cancels the terminal GRRP locally. when a service network element needs to acquire the reachability of the terminal group, sending, by the service network element, a terminal group reachability notification request message to a Home Subscriber Server, wherein the terminal group reachability notification request message comprises information of the terminal group; and when the HSS determines that the terminal group is reachable, notifying, by the HSS, the service network element that the terminal group is reachable; wherein the operation that the HSS determines that the terminal group is reachable comprises: after the HSS receives the terminal group reachability notification request message, the HSS sets a terminal group reachability request parameter, GRRP, locally, and forwards the terminal group reachability notification request message to an MME; and after the MME receives the terminal group reachability notification request message from the HSS, when the MME locally detects, according to the information of the terminal group, that a Paging Proceed Flag of a representative terminal of the terminal group has not been cancelled, the MME determines that the terminal group is reachable, and the MME notifies the HSS that the terminal group is reachable; and after the HSS receives the notification that the terminal group is reachable, the HSS cancels the terminal GRRP locally; or when the MME detects that the PPF of the representative terminal of the terminal group has been cancelled, the MME sets the terminal GRRP locally, and after the MME locally detects an activity event of the representative terminal of the terminal group according to the information of the terminal group, the MME sends a terminal group activity notification message to the HSS and locally cancels the terminal GRRP; and after the HSS receives an update location message of the representative terminal of the terminal group or the terminal group activity notification message from the MME, the HSS determines that the terminal group is reachable, and the HSS cancels the terminal GRRP locally.