Abstract: The Deep Space 3 is a proposed mission by NASA within the New Millennium Program. This paper primarily studies the relative state parameters autonomous determination of three satellites formation of the Deep Space 3 using inter-satellite relative measurements of like-GPS carrier phase and a ranging code onboard. To validate this inter-satellite relative measurements technique, various kinds of measurement projects and the accuracy of measure were researched. Firstly, the inter-satellites relative measurements system model of three satellites formation was built. Secondly, various kinds of measurement projects were simulated using high accurate pseudorange and carrier phase onboard. The single different phase bias was initialized with more epochs of pseudorange and phase observations during the relative attitude rotation among the satellites and the optimal initializing projection was investigated. Lastly, the results of simulation/covariance analysis were given.