Abstract: To investigate the aero-heating environment of distributed insulation tiles on re-entry flight vehicles, integrated coaxial thermocouples of only 0.3 mm in diameter are utilized to measure the heat flux at high Mach numbers. Intense interacted flow may prevail in interested regions such as the gap corner with small curvature radius. This makes it difficult to measure the heat flux. The curvature radius of the gap corner, height difference between insulation tiles, gap width, boundary layer state and Mach number are investigated to determine the influence on the aero-heating environment. Temporal signals are analyzed to obtain fluctuation characteristics of the transient heat flux. Results show that the inverse step leads to obvious heat flux rise. Difference in boundary layer state means notable discrepancy in the heat flux distribution over the gap corner. Higher Mach number induces less fluctuated heat signals and moderate heat flux. Negative heat flux phenomena emerges under some conditions. Results are useful to TPS design of insulation tiles, and increase the knowledge of the mechanism of the complex flow induced by gaps and steps.