Abstract: The states determination of formation constellation is an important research task. CPS is a chief means, which uses two observational signals： pseudo-range with an accuracy of 10 m, and carrier phase with an accuracy of 10^-3 m. Benefiting from AFF （Autonomous Formation Flying） technology, an assistant means ＂CPS-like＂ ranging technology is introduced to improve the states results, which can provide more accurate relative measurement information that are owed to shorter pseudo-code length and wavelength of carrier phase comparing to that of CPS technology. The states determination problem with double-satellite formation constellation for the earth-observation purpose is dicussed. The mathematical model combines ＂CPS-like＂ ranging technology with CPS is developed. Single GPS inter-satellite integer ambiguity and single ＂GPS-like＂ intra-satellite integer ambiguity are quickly and simultaneously initialized. Finally, these models above mentioned are simulated. The results of our tests indicate the formation states are improved significantly, with the accuracy of relative position reaching 10^-3 m and the accuracies of absolute attitudes reaching 10^-4 rad. The method proves to be valid through simulation.