Thermal analysis techniques were applied to investigate the reaction characteristics of a slow-propagation tungsten type delay composition system by means of differential scanning calorimetry (DSC) and thermogravimetry (TG). The ingredients of the delay composition were tungsten, barium chromate, potassium perchlorate, diatomaceous earth, and Viton. A formula of delay composition with a weight percentage of W/BaCrO4/KClO4/ D. E./Viton-27:54:11:6:2 has been used in a self-destruction mechanism of fuse, which was set as the original formula. In the first place, the reaction heat and weight loss for different compositions without Viton were measured during the reaction. The influence of each ingredient of the formula on the reaction system was analyzed from these experimental results. Afterward Viton was added in the samples of experiment to measure and analyze the influence of Viton on the reaction system. Finally, 28 experimental formulas of delay composition were designed on the condition that the weight percentage of Viton was kept constant and the maximum variation of weight percentage of all the others was limited within 20%. The delay compositions of various formulas were granulated and then the variations of reaction characteristics were measured to analyze the influence of weight variation of each ingredient on reaction characteristics. The results of this study are very important and useful for improving the self-destruction mechanism of fuse.