The invention relates to a preparation method of a polycrystalline silicon ingot. The method comprises the following steps: (1) a binding agent, a dispersing agent, and silicon particles of which the purity is above 99.9 percent and the diameter is between 1 [mu]m and 5,000 [mu]m, are added into deionized water, a pulp is obtained after uniform mixing, and the mass percentage of the silicon particles in the pulp is not less than 50 percent; (2) in a quartz crucible with a silicon nitride coating on the inner surface, the pulp is applied on the surface of the silicon nitride coating through spray coating, roller coating or brush coating, so as to form a pulp layer with a thickness between 1 mm and 10 mm; the crucible with a silicon coating is obtained after drying; (3) the crucible with the silicon coating is sent into a polycrystalline silicon ingot furnace after being loaded with silicon materials, the silicon materials are heated after vacuum pumping, a silicon material melt is cooled for polycrystalline silicon growth after the silicon materials are completely molten, and the polycrystalline silicon ingot is obtained through annealing cooling after the polycrystalline silicon growth is completed. The polycrystalline silicon ingot obtained through the method can be used for the manufacturing of a solar battery, so that the average battery efficiency of a silicon wafer exceeds 18 percent.