The invention relates to a microcapsule suspending agent and a preparation method of the microcapsule suspending agent. The microcapsule suspending agent comprises the following components by weight:1.0 part of 50% by mass of pyrethrin crude oil, 1.25 parts of 40% of a rotenone drug substance, 6.75 parts of a mixed solution of cyclohexanone and dimethylbenzene, 2.25 parts of an emulsifying agent,0.75 parts of toluene-2,4-diisocyanate, 0.375 parts of glycerol, 78 parts of a polyvinyl alcohol aqueous solution with the concentration of 0.5 % by mass and 10 parts of an organic acid. The microcapsules are of a spherical shape, and the mean grain size of the microcapsules is 20.78 plus or minus 0.39mum. The preparation method of the microcapsule suspending agent is simple and comprises the following steps: after dissolving core materials, dispersing the dissolved core materials with the emulsifying agent and toluene-2,4-diisocyanate in the polyvinyl alcohol solution, then adding glycerol, forming capsules, and regulating a pH value to prepare the microcapsule suspending agent. The microcapsule suspending agent has a better and more durable preventing and curing effect on aleurodicus dispersus russell and phyllotreta striolata than that of the existing rotenone missible oil and pyrethrin missible oil.