Abstract: For the engineering surface heat flux estimation problem, it is often expected to roughly and quickly account the estimation error according to the measurement accuracy in advance so as to optimize the measurement system. So, in this paper, the estimation error of the heat fluxes with single frequency are quantitatively analyzed and a response surface model between the estimation error and the frequency and measurement accuracy is built. Furthermore, the cases of multiple-frequency combined heat flux are concerned, and due to the frequency analysis it is shown that the low-frequency component can be inversed with high accuracy and the high-frequency component is the key reason leading to the estimation error. Then, the estimation error can be roughly accounted through the function of the estimation error with respect to measurement accuracy under high-frequency circumstance. Based on this idea, the heat flux components with different frequencies are transformed and uncoupled in the frequency fields, and by utilizing the Parseval's theorem, the power percentage of the components can be calculated and employed to develop the estimation error accounting method for the combined heat flux. Finally, some examples are presented and the results show that the error accounting method is feasible and effective.