To enable the dual-mode scramjet engine operate in the whole flight trajectory, the urgent development of the Rocket Based Combined Cycle (RBCC) propulsion system has been put forward. The behavior of ram-scram combustion mode transition was examined using direct-connect experiments of a model RBCC combustor along with pressure measurements. At an inflow stagnation condition of P-0 = 1.5 MPa and T-0 = 1280 K, four combustion modes, namely weak combustion mode, rocket-scram mode, rocketram mode and ram mode were classified through wall pressure distributions, combustor inlet Mach number, and flame plume visualization. Both the position of fuel strut injectors and the cavity installation location had a significant effect on RBCC combustion modes. When rocket jets were added, the change of the fuel strut position could cause mode transition. Furthermore, as the rockets were turned off, different locations where the cavities were installed could lead mode transition as well. When the primary heat release zone was stabilized at the downstream in the combustor, the addition of rocket jets would make the burning zone jump to upstream abruptly. The discovery of this phenomenon provided a new method and feasible strategy for mode transition. (C) 2017 Elsevier Ltd. All rights reserved.