BeiDou Navigation Satellite System transmitted radio signals based on the space vehicle to provide positioning, navigation and timing service, short message service and international satellite search and rescue service for the global user on earth, ocean and even space. It introduces comprehensively the construction process from BeiDou 1st generation, 2nd generation and 3rd generation. And also the components of BDS space segment, ground segment and user segment are described in detail. Finally the typical applications of BDS such as intelligent transportation, logistics, precision agriculture and disaster mitigation and rescue are discussed individually.