Disclosed are a method and apparatus for monitoring User Equipment (UE) reachability in a wireless communication system. More specifically, a method for monitoring UE reachability in a wireless communication system comprises receiving, by a Mobile Management Entity (MME), a message for monitoring the UE reachability including UE reachability related indication from a Home Subscriber Server (HSS); and allocating, by the MME, an Active Time to a UE, wherein the UE reachability related indication is used for setting the Active Time of the UE and wherein the UE reachability indication is used for the UE to stay reachable so that downlink data that a server wants to transmit to the UE can be transmitted to the UE.