Nowadays, the research and application about delay-tolerant network (DTN) have become more and more popular. DTN is a new kind of network derived from deep space communication. differed with traditional network, DTN network has the folowing everal characteristic; long delay, limited resources, interal connectivity, asymmetric data rate, low signal to noise ratio, and high error rate. in this paper, we present the development and basic characteristic of DTN, and discuss the network architecture in details. in addition, the issues of reability transmission, congestion control, security and applications are also be covered in this paper.