An embodiment of the present invention discloses a method and related device for monitoring the quantity of user terminals, wherein the method comprises: a monitoring device receiving a notification message reported by a transmission device regarding the detection of a transmission event, the notification message carrying a policy identifier; the monitoring device increasing a statistical number of times corresponding to the policy identifier by one; and the monitoring device performing a transmission control over the transmission event when the statistical number of times is greater than a threshold value of the number of user terminals associated with the policy identifier. According to the present invention, it is possible to monitor the number of user terminals associated with the transmission event and to perform the transmission control over the transmission event exceeding the threshold value of the number of user terminals, so as to save the transmission cost, in a case where the transmission event is
