Abstract: An intensity-based method for direct heat flux measurement with double-layer temperature-sensitive paint (DL-TSP) lattices has been proposed in this study. With the aid of an accurate spray technique, temperature-sensitive paint lattices L3 and L1 are sprayed in a staggered arrangement on the upper and lower surfaces of a transparent film L2 of uniform thickness, respectively. Utilizing image edge detection and interrogation of particle image velocimetry (PIV) to locate the lattices, the light intensity of spray points of the temperature-sensitive paint can be extracted, and the corresponding temperature distributions of L1 and L3 can be obtained from the light intensity-temperature calibration relation. The heat flux is calculated using both the Cook-Felderman method and the Fourier’s law, which are compared with data from the heat flux sensor. The applicability of different methods is analyzed based on the thermal penetration time. The results indicate that the double-layer temperature-sensitive paint lattice method can not only capture the transient heat flux under short-term thermal shock using the Cook-Felderman method, but also measure the long-term steady-state heat flux using the Fourier’s law. The present method has certain application prospects in the heat flux measurement of high-speed flows.