The invention relates to an efficient straw degrading composite fungicide (JFB-1) and an organic fertilizer preparing method thereof. The composite fungicide comprises composite bacteria and a carrier, wherein the carrier is wheat bran, and the composite bacteria include composite bacteria I, composite bacteria II, composite bacteria III and auxiliary bacteria. The composite bacteria I, II and III account for 1-1.5% of the weight of straws, wherein the composite bacteria I account for 20-25%, the composite bacteria II account for 45-50%, the composite bacteria III account for 30-35%, and the composite bacteria are added uniformly in compost fermentation so as to effectively improve the maturation speed and the quality of an organic fertilizer. The fungicide is fully mixed with straws of rice, asparagus and other crops to carry out compost fermentation, the straws can be degraded rapidly through the synergistic effect of the bacteria, the degradation efficiency is improved, the degradation time is shortened, and insect pests are effectively killed and are rapidly transformed into the organic fertilizer for improving soil. The efficient straw degrading composite fungicide can be used for effectively solving the problem of land occupation caused by landfill, or the problems of fire, traffic dangers, environment pollution and the like caused by burning.