In this paper, thermogravimetric analysis (TGA) of crude glycerol, date seeds and their blends in was performed. Blending solid biomass with crude glycerol is found in the literature to enhance the gasification of solid biomass and yield valuable syntheses gaseous fuels. The studied glycerol to date seeds ratios were [3:1], [1:1] and [1:3] respectively. The samples were heated from room temperature till 700°C at a ramp heating of 20°C/min in nitrogen environment supplied at 50 ml/min. The used crude glycerol was prepared from waste cooking oil. In addition, theoretical curves based on the proposed ratios were done and their results were compared to the experimental work. The main objective of this work is to study the effect of the glycerol content on the thermal degradation performance of the prepared samples. The results have shown that the crude glycerol presence in the blends has affected the TG behavior and implied some kind of chemical reaction occurring in the temperature range of 200°C to 475°C. Also, the theoretical curves had shown almost good agreement with the experimental ones specially at high temperature levels (475°C to 700°C) and indicated some kind of chemical reactions between the raw materials at lower temperature levels (200°C to 475°C).