Abstract: Thin-skin calorimeters, coaxial thermocouples and infrared thermographics have the problems of being sensitive to the noise and high uncertainty in the corresponding measured heat flux densities, though frequently used in hypervelocity low-density wind-tunnel tests, The problems result from the complicated measuring principles and their low sensitivities. Hence, taking the properties of high sensitivity and ease of use into account, atomic-layer thermopile (ALTP) heat-flux sensors and small-sized Schmidt-Boelter gauges, two kinds of temperature-difference-based heat-flux sensors, are used to measure the low heat flux in a long duration, and their good performance is confirmed by the experiment conducted in a hypersonic low-density wind tunnel. Meanwhile, considering the fact that the size in diameter is relatively too large and the sensitivity is dependent on the effective length of the sensitive element, the sensitive elements of the ALTP sensor are connected in series by electric films, and the sensitivity of the revised ALTP sensor is multiplied without enlarging the size in diameter, which helps get small-sized ALTP heat-flux sensors in the near future.