The principles and the experimental results for temperature measurements by laser-induced predissociative fluorescence (LIPF) are presented. With a tunable KrF excimer laser, the fluorescence of OH radical was obtained in a methane-air flame at the pressure of atmosphere and the structures of the spectrum were analyzed. The temperatures in the flame were also measured by LIPF narrow-band and broad-band methods. By selecting proper excited lines, subtracting background noises and choosing moderate laser energy, both the precision is less than 3%.