The invention relates to a sulfur-doped molybdenum selenide negative composite material for a sodium-ion battery and a preparation method of the sulfur-doped molybdenum selenide negative composite material, and belongs to the technical field of sodium-ion batteries. The sulfur-doped molybdenum selenide negative composite material comprises sulfur-doped molybdenum selenide and a carbon nanotube, wherein the sulfur-doped molybdenum selenide is evenly deposited for growth on the surface of the carbon nanotube to form a three-dimensional conductive network. According to the preparation method, a molybdenum oxide evenly grows on the surface of the carbon nanotube through a hydrothermal synthesis method; with the molybdenum oxide/carbon nanotube composite material as a molybdenum source and a carbon source, the molybdenum oxide/carbon nanotube composite material is evenly dispersed into an alcoholic solution; a reducing agent, a selenium source and a sulfur source are added; the alcoholic solution is cooled and dried to a room temperature after hydrothermal reaction; and then the sulfur-doped molybdenum selenide negative composite material is obtained through high-temperature calcination treatment. The preparation method is simple, reliable, good in process repeatability, high in operability, low in cost and applicable to industrial production. The composite material shows high specific capacity and long cycling stability when applied to the sodium-ion battery.