In this paper, a single epoch algorithm for fixing the carrier phase ambiguity was presented to meet the speed and accuracy requirements of satellite dynamic attitude determination system. The algorithm was based on the nowadays available conditions of multi-frequency carrier-observations, two of them can form a wide-lane measurement. Then made sure of the wide-lane ambiguity by using existence constraint factors to limit the ambiguity search range by eliminating the incorrect ambiguity candidates through four methods. Finally, the integer ambiguity on the single-frequency carrier phase could be resolved. Compared with traditional TCAR, this algorithm wins a higher success probability of integer ambiguity determination. The simulation result indicates that this method is feasible and is suitable for single epoch ambiguity determination.