Abstract: Experimental results of heat transfer to rough walls are given here for sphere cone models at Mach number 5. The nose radius of the models is 27.4mm and base diameter 60mm. Five models have been tested with different roughness in its bead diameter range from 0 to 0.9mm. The tests were conducted in a conventional hypersonic wind tunnel at total pressures from 10kg/cm2 and Reynolds numbers ReD from 0.8×106 to 3.6×106.The test results indicate that the smooth wall model heating is the laminar flow heating, its heat flux at the stagnation point is quite close to the theoretical data, and the influence of roughness at low total pressure （10kg/ cm2） occurs mainly to promote the transition and development of a boundary layer. With the increasing total pressure in the wind tunnel the static pressure on model and local Reynolds numbers increase correspondently. In this case the effect of roughness on heat transfer becomes remarkable, and the most remarkable region appears at sonic point region on the nose. At the highest total pressure （pt =45kg/cm2） and with the largest roughness （d = 0.9mm） the ratio of rough wall heat flux to laminar flow smooth one could be up to 4 except at stagnation point, where it could approach 6. Its raise seems to be related to the local shape change in the vicinity of the stagnation point.