An analysis of main features of unsteady heat flux measuring in shock tubes experiments with a characteristic process time of ~1 μs - 1 ms using sensors based on anisotropic bismuth thermoelements is made. The heat flux behind the reflected shock wave and at the blunt body stagnation point has been measured. Testing of the heat flux calculation method was carried out. The difference between the experimental data and the theoretical value of the heat flux does not exceed 50%. The possible reasons influencing the magnitude of measurement uncertainty are analyzed. The experiments performed have shown the applicability of a sensor based on anisotropic thermoelements and the method for calculating the heat flux from its electrical signal for typical conditions of experiments on shock tubes.