Abstract: The disclosure provides a Femtocell network system coexistent with a universal mobile telecommunication system (UMTS) network and the deadzone effect alleviating method thereof. For each femto access point (FAP) in the Femtocell network system, a minimum transmission power is pre-configured. When an inadmissible user equipment (UE) performs a location update or a handoff process to obtain the access right to a closed FAP, at least a FAP gateway may estimate the probable existence of deadzone via the UE location update or handoff procedure. Before the inadmissible UE reaches the deadzone of the closed FAP, the transmission power of the closed FAP is decreased repeatedly to allow the inadmissible UE to receive the signals and messages from the UMTS network, until the closed FAP reaches a threshold of its minimum transmission power.