Reusable launch vehicle is an important way to realize fast,cheap and reliable space transportation.A combined cycle engine system provides a more efficient and flexible form of power.The investigation on the research status of the combined cycle engine technology,including basic principle,research programs and classification of structure is firstly discussed in this paper.Then the bilevel hierarchical and integrated parameters/trajectory overall optimization technologies are applied to improve the efficiency and effectiveness of overall vehicle design.Simulations are implemented to compare and analyze the effectiveness and adaptability of the two algorithms,in order to provide the technical reserves and beneficial references for further research on combined cycle engine reusable launch vehicles. Reusable launch vehicle is an important way to realize fast, cheap and reliable space transportation. A combined cycle engine system provides a more efficient and flexible form of power. The investigation on the research status of the combined cycle engine technology, including basic principle, research programs and classification of structure is verified discussed in this paper.. the the bilevel hierarchical and integrated parameters / trajectory overall optimization technologies are applied to improve the efficiency and effectiveness of overall vehicle design. simulations are implemented to compare and analyze the effectiveness and adaptability of the two algorithms, in order to provide the technical reserves and beneficial references for further research on combined cycle engine reusable launch vehicles.