The invention discloses bio-organic fertilizer. The bio-organic fertilizer is fit to be base fertilizer of the legume crops, and is prepared by taking sugarcane powder, straw, fishpond bottom mud, rice bran, turf, rape seed cake, chicken manure, sheep manure, fishbone dust, ammonium sulfate, copper sulfate, ammonium molybdate, sodium selenite and the compounded microbial agent as the raw material;and a preparation method comprises the following steps: crushing the straw and the rape seed cake, sterilizing together with the sugarcane powder, the fishpond bottom mud, the rice bran, the chickenmanure, the sheep manure, and the fishbone dust, and then replenishing water, uniformly stirring, blending the microbial agent into the mixture to ferment, blending the turf, the ammonium sulfate, thecopper sulfate, the ammonium molybdate and the sodium selenite in the mixture after the fermentation is finished, and uniformly stirring to obtain the bio-organic fertilizer. The bio-organic fertilizer disclosed by the invention can provide the vast majority of nutrient for the growth of the legume crops, and the raw materials can be effectively matched to improve the growth speed of the legume crops; and meanwhile, the soil structure can be effectively modified, a soil granular structure is changed, and the adsorption capacity of the soil is increased.