As accelerated development of BeiDou satellite navigation system, it become more and more urgently to test and estimate the performance of the system. Therefore, the Chinese Academy of science constructed the outfield testing platform of BeiDou satellite navigation system. The platform contains space segment which consists of GEO satellites and ground segment that had functions including producing/transmitting/receiving navigational signals, analyzing/estimating signal quality, establishing/maintaining the standard of time, and measuring/predicting orbit of satellites. At present, the constructing of platform is finished. The platform has the characteristics of comprehensive functions and flexible configuration, so it can simulate operation of actual satellite navigation system, and have the entire ability to simulate and estimate the satellite navigation system. In the future, the platform will collaborate with other GNSS in the world, trying to build the platform together to test new navigational technology, and support the researching of new navigational signal structure, new-style applied model, out-door and in-door seamless navigation and so on, as well as participating in the associate observation of GNSS satellites, sharing the observe data, and training the technical personnel of satellite navigation. We will promote the platform to become the international large and open GNSS testing platform and contribute to the international development of GNSS.