Abstract: In order to improve the performance of frame synchronization in adaptive frame length advanced orbiting system (AOS), a scheme of synthetical frame synchronization is proposed. In this synthetical scheme, the probability of false loss relating to the bit error rate and the probability of false alarm relating to the model of attached sync maker (ASM) are considered synthetically. Then the performance formulas of synthetical frame synchronization are given and analyzed to obtain the relevant frame synchronization parameters. At last, the performances of the synthetical frame synchronization scheme and the basic frame synchronization scheme are simulated and compared. The results show that performance of the synthetical frame synchronization scheme precedes the basic frame synchronization scheme markedly.