The objective of this study is to investigate and analyze the tar yields and structural changes of tar formed during a high temperature thermal cracking process. Experiments were conducted in order to study the effect of temperature on the yield and characteristic chemicals of tar. All experiments were carried out with parawood under steady-state conditions. The temperature of the pyrolyzer was controlled at 600 degrees C and pyrolysis gases were carried to the reformer by nitrogen. The thermal cracking tests were performed at six different temperatures: 700, 800, 900, 1,000, 1,100, and 1,200 degrees C. The samples of tar were analyzed by gravimetric analysis, gas chromatography-flame ionization detector, and gel permeation chromatography techniques in order to get information and an understanding about the tar, such as tar yield, compositions, and average molecular weight. From the experimental results and quantity analysis, the amount of tar decreased continually to 90% reduction as temperature increased from 600 to 1,200 degrees C resulting from thermal cracking of tar into the lighter products. In chemical analysis, at a low temperature range, the aromatic compounds were dominant in tar compositions. Meanwhile, these phenomena were adverse at higher temperatures and polycyclic aromatic hydrocarbons dominated. These resulted in higher than the average molecular weight as the temperature increased.