This Diploma Thesis is focused observation of color and chemical changes of fir wood samples after thermal degradation. We have used fir wood samples size 150 x 100 x 100 mm (Length Width Thickness). Samples were gradually exposed to temperatures: 20, 100, 150, 200, 220, 240, 260, 280 a 300 °C for 5 hours. Intoruction of the thesis defines the theoretical knowledge on the subject. In practical part based on laboratory research, is by graphs and charts is evaluated the impact of temperature on color changes and pecentage of basic components of fir wood. It was subsequently evaluated interdependence of color changes and percentage of basic components of wood after thermical degradation. The results obtained indicated, that temperature influences color and chemical composition of the wood. Thermal load affecting the color changes dE specific clearance L and colorful components a, b. The effect of increasing the temperature increases the percentage of the cellulose, lignin and extractives, hemicellulose and holocellulose content decreased.