The invention relates to a method for improving the fruit-bearing rate of castor-oil plants, belonging to the technical field of plant culture. The method comprises the following steps: firstly, preparing a basic reagent comprising 3% of N, 2% of P, 1.5% of K, 1.0% of Zn, 1.5% of Mn, 2.5% of Fe, 0.5% of B, 8% of porous phyllosilicate, 2.5% of peat, 2.5% of grass carbon, 15% of humic acid and 60% of water; then, adding the following viable counts of microbes into each 100g of basic reagent to be mixed into a seed soaking agent: 2.8*1010 Bacillus megaterium, 4*1010 Azorhizobium caulinodans, 3.2*1010 Paenibacillus polymyxa and 2.6*1010 Bacillus subtilis; diluting under the condition that the ratio of the seed soaking agent to the water is 1:200 to obtain diluted seed soaking liquid; and soaking seeds in the diluted seed soaking liquid for 20-24h, fishing out the seeds, accelerating germination at 28-30 DEG C, and sowing when the seeds germinate. The effective capsules of the individual castor-oil plant are increased by more than 30%.