For the general application of liquid crystal thermography on film cooling measurement, two separate tests with different injection flow temperature rises are conducted under the same Free-stream temperature and flow conditions. Therefore, a pair of equations for the two separate test conditions is solved to obtain heat transfer coefficient and film cooling effectiveness. An error could possibly occur in evaluating the film cooling effectiveness if an improper pair of injection temperatures was chosen. To reduce the data reduction error, a better mean to select an adequate pair of heated injection temperatures is recommended in current study. (C) 2001 Elsevier Science Ltd. All rights reserved.