Ultraviolet-visible (UV-Vis), infrared transmission reflection absorption (RA) and ATR spectra were used to study the mono-and multi-layer Langmuir-Blodgett (LB) films of C12H25ONaph (1,5)OH at various temperatures to investigate dependencies of the aggregation and phase transitions on the number of monolayers. The UV-vis spectra of the LB films revealed that C12H25ONaph (1,5)OH forms aggregates in the LB film. From the temperature dependence of UV-vis absorption spectra, it is clear that the aggregate was gradually converted to monomer with the temperature increased. A comparison of the infrared transmission and ATR spectra reveals that the hydrocarbon chains were tilted considerably in the LB film.