In this paper, in order to improve the small satellite's positioning precision under constellation mode, we discuss a methed to deal with whole network datum of psecdocode measuring distance of GPS carried on the satellites, based on decreasing or eliminating error by difference between satellites and introducing the network restraint of constellation. After that, an actual example is given. Finally, we present several presumptions aiming at small satellite constellation's measurement and control, while not relying on GPS and raising the independence of small satellite constellation's positioning.