The invention relates to a composite microorganism oil-displacing agent for improving the oil recovery rate. The composite microorganism oil-displacing agent is prepared by adding mixed liquid containing 1-8 percent of byproducts of triticeae crops, 1-8 percent of byproducts of maize, 0.5-6 percent of byproducts of wood and the balanced of water by weight into 5-10mg/L trace element and 300-500mg/L polyacrylamide, wherein the particle diameters of the byproducts of crops and wood are smaller than 0.5 mm. The composite microorganism oil-displacing agent is filled with the aid of oxygen-containing air, has dual functions of providing nutrition for microorganism and plugging a high permeability zone, can enlarge the swept volume of nutrient fluid and the fermentation range of the microorganism, prolong the acting time between the microorganism and rock and fluid in an oil layer, satisfy the requirement for fermentation time, provide conditions for biological action and biochemical actionand improve the whole effect of microorganism oil recovery, e.g. the recovery rate is increased by 12-15 percent based on water drive.