Abstract: A body flap is usually arranged on the base of the plane-symmetry reusable launch vehicle with the longest moment arm for the need of pitch balancing control. Jet interaction from main engine with body flaps is an important problem that cannot be ignored in the design of reusable launch vehicles, which would cause severe regional heating of the flaps and increase technical difficulty of thermal protection design. In this paper, the high temperature jet interaction with the body flaps was studied in a combustion gas flow wind tunnel experiment, and jet heating characteristics of direct acting and secondary interference were obtained and analyzed. Then, numerical simulations on the complex jet interaction flow field for typical flight conditions were carried out using a multi-species frozen model which is verified by the experiment data. Finally, correlation analyses of heat flux and flow field characteristics both for the jet direct acting and secondary interfe-rence were performed, by which the jet heating main controlling factors and correlations were obtained for two different interference types. Such method is very effective to realize a fast and accurate jet heating prediction for a reusable launch vehicle.