Abstract: High-frequency fluctuation heat-flux is one of the key quantities in experimental investigations on basic aerodynamic problems related to hypervelocity boundary layer transition and shock wave/boundary layer interaction. Currently, the measurement of high-frequency fluctuation heat flux can be achieved with Atomic Layer Thermopile (ALTP) heat-flux sensors. Different from the pulse laser deposition technique, ALTP sensors with a higher sensitivity and faster response time are developed by the metal-organic chemical vapor deposition technique with optimized technology parameters. To achieve a higher sensitivity, multiple YBCO (YBa₂Cu₃O_7-δ) films, the sensitive element of the ALTP heat-flux sensor, are connected in series by conductive films. Discussion on the tradeoff between high sensitivity and fast dynamic response is helpful for developing small-sized ALTP sensors with optimized performance in the near future. In view of the limited temperature tolerance of the YBCO film, a new generation of ALTP sensors based on LCMO (La_1-xCa_xMnO₃) is developed and calibrated after a test in a high temperature environment. Similarly, multiple LCMO lines are alternately connected in series by conductive lines, because LCMO can function as a semiconductor to alter its electrode polar. Then more LCMO lines can be placed on the sensitive surface of the same size. Flexible sensors are required, when the models have a curved surfaces. But inclined SrTiO₃ slice, that is the substrate of general ALTP sensors, cannot be buckled. Hence, flexible ALTP sensors are developed, in which a flexible Hastelloy C-276 film with an MgO interlayer is used as the substrate. The static calibration result of about 2.81 μV/(kW·m⁻²) shows the potential. Because ALTP sensors have good characteristics of fast response time, they are frequently used in shock tunnels and quiet hypersonic wind tunnels to help experimentally investigate the basic aerodynamic problems. Moreover, ALTP heat-flux sensors have high linearity, while its output is directly proportional to the input heat flux. Hence, ALTP heat-flux sensors can be used to measure the average heat flux. Its application in hypervelocity low-density wind tunnels confirms that ALTP sensors are valuable, especially since considering the frequently-used thin-skin calorimeters, coaxial thermocouples and infrared thermographic method have the problems of being sensitive to the noise, short effective time, and high uncertainty. Furthermore, ALTP heat-flux sensors can be used for on-line calibration of thin-film resistance gauges and coaxial thermopiles in shock tunnel tests, as since the frequently-used two-stage calibration method has a higher uncertainty.