While in situ TLC/FTIR technique has tremendous potential in the analysis of complex mixtures, the conventional stationary phase, such as silica gel, used for TLC/FTIR analysis, has strong absorption in IR region and thus brings about severe interference in the obtained FTIR spectra of the separated samples. In this work, we propose to use lanthanum fluoride fine particles as a new stationary phase of a TLC plate. The average size of LaF3 particles is around 100 nm. FTIR spectrum of the LaF3 particles has no interfering absorption. Preliminary TLC experiments show that mixtures of rhodamine B and methylene blue mixture can be successfully separated by this new TLC plate using LaF3 fine particles as a stationary phase. Methylene blue and rhodamine B from separated spot can be clearly detected by using in situ FTIR spectra.