Sulfate-rich belite sulfoaluminate cement is used in rapid construction of marine engineering, but the strength of the clinker developed is not enough in the later period. The improvement of the strength in the later stage was investigated via boron/phosphorus composite doping. The effect of boron/phosphorus composite doping on the mineral formation, microstructure, and hydration of high sulfur belite aluminate clinker was analyzed by X-ray diffraction combined with Rietveld full spectrum quantitative analysis, scanning electron microscopy, isothermal calorimetry and thermogravimetric analysis. The results show that boron and phosphorus both can exist in the crystal structure of dicalcium silicate, form the crystal defects, and increase the content of α-C2S and c-C4A3$, thus promoting the early hydration and later strength development of the clinker.