The function of water and waste system (WWS) of civil aircraft is to provide the potable water, washing water and toilet flashing water for the flight members and passengers in the flight, to disposal the waste water at the same time. The location of the WWS Components and lines cross the the FWD EE bin to the AFT WWS compartment along the airframe. Temperature distribution is complex among different zones. The system will lose function due to icing without icing protection when in low temperature. The heaters location is an emphasis and difficult to confirm. This document analyzes the temperature of different zones using the module analysis method to confirm the icing protection areas, the electrical heater location confirming rule. To make the icing protection efficiency maximum, the document gives the approciate icing protection method for different components. At the same time, this document also provides the heater electrical power calculation for hose, line and tank. The icing preotection method in this document can provide the reference for civil aircraft WWS design without the aircraft temperature distrbution.