Olives pomaces wastes (OPW) pyrolysis behaviour was studied using thermogravimetric analysis under inert conditions. Nitrogen flow effect on OPW thermal degradation was illustrated and discussed. Thermal residence time, peaks numbers, the maximum temperatures and the conversion rates were determined and compared. For 20 and 100 ml/min, a small peak appears at 110°C, after 36 min of heating. It corresponds to the olives pomaces water evaporation. There are two major peaks in the derivative thermo-gravimetric curves. The first peak corresponds to the hemicelluloses thermal decomposition under pyrolysis conditions. The second peak corresponds to the cellulose and lignin thermal decompositions.