Abstract: Many of the convection heat transfer process are involved in the research of nuclear reactor thermal hydraulics. To experimentally determine the variation of the temperature filed in those processes is important for the design and safety operation of the nuclear reactor. The application of the two-color planar laser induced fluorescence（PLIF） in the measurements of fluid temperature distribution is discussed in the paper. The laser dyes used here is rhodamine B（RhB） with negative temperature coefficient and fluorescein 27（Fl27） with positive temperature coefficient. The beam of the laser light is adjusted to laser sheet by using the lens group. The fluid with dyes is excited by this laser sheet in a specific plane and temperature dependent fluorescence is released. The temperature field of the plane can be determined through the intensity information. Some technical aspects encountered in the application of the two-laser PLIF are discussed in the paper, such as the spectra characteristic of the dyes and the separation of the spectra. The calibration temperature is higher than the water saturation temperature（at atmosphere pressure）.