As main by-product of semi-dry desulfurization technology, desulfurization ash is very difficult in utilizing and cost consumable, which cannot be disposed in direct stacking and landfill, causing environmental pollution and the waste of potential resources. Carbon black (8 000 yuan·ton-1) and white carbon black (6 000 yuan·ton-1), as the commonly used rubber reinforcing filler, can only be prepared by using complicated process and always leads to large consumption of energy and resources, resulting in higher costs. Thus, the development of desulfurization ash into low-cost inorganic rubber reinforcing fillers has become one of main methods to achieve the sustainable development of resources and enhance economic performance by using high value-added utilization of solid wastes and reduce cost of fillers in rubber industry to a great extent, respectively. The desulfurization ash is organic while rubber is inorganic. Therefore, it is necessary to conduct chemical modification for desulfurization ash to weaken incompatibility of interface (organic/inorganic) between them. In this paper, the modified desulfurization ash was prepared by silane coupling agent Si69, silane coupling agent KH550 and desulfurization ash. Then, composite rubber was prepared by replacing part of carbon black with modified desulfurized ash. Next, mechanical properties of composite rubber, such as tensile strength, tear strength and shore hardness of composite rubber was tested by referring to national and industry standards. Specially, microstructure of composite rubber was characterized and analyzed by scanning electron microscope (SEM), composition structure of modified desulfurization ash was characterized and analyzed by using fourier transform infrared spectrometer (FTIR), and mineral composition of modified desulfurization ash was characterized and analyzed by using X-ray diffractometer (XRD), so as to reveal the modification mechanism of both agents as well as reinforcement mechanism of desulfurization ash for composite rubber. The results show that when desulfurization ash was modified by applying both silane coupling agent Si69 and silane coupling agent KH550, the best enhancement effect occurs with tensile strength, tear strength and shore A hardness as 20.36 MPa, 45.71 kN·m-1 and 66, separately. The desulfurization ash is modified by combined action of both silane coupling agent Si69 and silane coupling agent KH550 not only can still maintain good alkalinity, which can enhance reinforcement effect of composite rubber, but also can improve surface property and structure of desulfurization ash, so as to enhance the compatibility of organic/inorganic interface between modified desulfurization ash and styrene butadiene rubber.