The determination of the local convective heat transfer coefficients on test surfaces from the measured data of temperature or heating time by liquid crystal thermography often requires the neglect of heat conduction along the plane of the test section. The influence of tangential heat conductivity on temperature measurement by liquid crystal thermography has been investigated numerically by comparing temperature or heating times in a test section with or without tangential conduction. Results show that the neglect of tangential conduction can change the deduced local convective heat transfer coefficient by nonsteady thin wad technique by 10% at sensitive spots where large gradients in convection coefficients appear. The corresponding error by the nonsteady thick wall technique can be over 20% and by steady hot-film liquid crystal thermography may be more than 100%.