This study carried out to examine effect of thickness and temperature of meat on the spectrum using fiber optic probe in NIR analysis. The spectra of beef had two characteristic peaks at 750㎚ and 970㎚. There were eight obvious peaks(Q-H, N-H, C-H band) in the second derivative spectra. There was nonlinear positive dependency over 9.05㎜ of sliced hams thickness and the energy absorption. Increased absorbance was observed from 0.040 to 0.700 of the frozen raw beef round spectrum to 9.3㎜ at 970nm. The penetration depth of NIR into meat was estimated to be 10㎜. When rheological changes by temperature were examined, an outstanding distinction between frozen sample and chilled samples was found at the water peak area of 970㎚. The energy absorption at 750㎚ deceased upon increasing the temperature in the second derivative spectrum. The results indicate that NIR was a very useful instrument for the analysis of meat components. However, the analysis of beef with high moisture needs temperature control.