The invention relates to the technical field of sludge treatment, in particular to a sludge drying system based on biomass energy. The sludge drying system includes a precipitation device, a dehydration device and a drying device which are successively arranged, the precipitation device, the dehydration device and the drying device are connected in series by a conveying device, and the drying device is connected with a hot air device. The sludge drying system is optimized in technological process, sludge drying is carried out by adopting a mode of drying after mechanical dehydration, and gooddehydration effect can be realized; and clean energy is used, the hot air device does not pollute the environment in the process of heat production, at the same time, smelly gas generated in other processes is also solved, harmless treatment of sludge and recycling of resources are realized, and the purposes of energy saving, emission reduction and environmental protection are achieved.