Using the Taguchi method, this study analyzed the optimum conditions for preparing the solid fuel briquette of the rice straw by a piston-mold process. The controllable factors used in this study consisted of the following: (1) the type of binder (such as the rice bran, the soybean residue, and the sawdust of Acacia confuse), (2) the hot-pressing temperature (such as 110, 130, and 150 degrees C), (3) the size of the smashed rice straw (such as 10-5 mm, 52 mm, and < 2 mm), and (4) the percentage ratio of rice straw to binder in a briquette (such as 100/0, 80/20, and 60/40). The percentage contribution of each controllable factor was also determined. The confirmation experiment was carried out according to the optimum conditions. Most interestingly, the size of the smashed rice straw is the most influential factor to solidify fuel briquette, and its value is up to 43.0%. (c) 2009 Elsevier B.V. All rights reserved.