Nowadays, the majority share of the Internet traffic is contributed by video streaming services. Due to the growth of Internet bandwidth, it is possible to provide HD live streaming services on the Internet which will be a trend in the near future. As the population of the users of HD live streaming services increases, the bandwidth will become a problem again. Centralized-based systems are not suitable for such services any more, and P2P architectures will be a possible solution. However, live services have strict constraints on playback delay and upload bandwidth. Conventional design principles for P2P systems need to be modified to fit the new situations. In this paper, we give an analysis on HD live streaming services and point out some unique design principles for such systems. Based on the principles, we proposed a system design for P2P HD live streaming systems. Also, a prototype is developed to demonstrate our design and be the platform for our future researches. Meanwhile, some implementation details are also introduced to facilitate and inspire future research works in the community.