Absorption spectra of aggregates of dye Langmuir-Blodgett films were investigated in different conditions. The typical aggregate of dye MOC (1-methyl-l -octadecyl-2,2 -cyaninpereh-lorate) appears an absorption band (J band) peaking at near 580 nm with absorbanoe of 0.09. The temporal effect of a new sample shows that it takes about 2 hours for the aggregates to be stable. Several parameters of J band of samples were measured, such as absorption peak position, absorbanoe and the width of band, as well as the temperature dependences of their parameters. The inyertibl? variation of the absorbanoe versus temperature in a physioal basic for the aggregate LB layer to "be used in optical storage. When the sample was heated at temperature over 100 ℃ the thermal invertibility of absorption broke down indicating a phase change.