ABSTRACT:UPS is a kind of device that can store energy,its key part is anti-change device,it is an equipment which can keep the output of voltage and frequency constantly, which is a core link in power supply system.The technique development of the UPS will concentrate on the intelligent network power supply—expands the application of UPS;Adopting IGBT can heighten work efficiency, prolong the battery life;the technique of power supply redundancy can increase the work stability so as to assure the and guarantee the UPS dependable.Considering the economic and practical reason,this subject is mainly to research and design the Off-line and intelligent UPS. In order to finish this design well,I will choose the Single Chip Microcomputer 8031 to control this UPS and use language C to edit procedure,it can ensure the UPS work dependably and controlled easily.