The invention relates to a method used for preparing a biological insect trapping bait through fruit fermentation. The method comprises following steps: defective fruit raw materials are crushed to prepare fruit jam, the fruit jam is uniformly mixed with sugar and water to prepare a fruit pulp, and the fruit pulp is introduced into a sterilized container; the fruit pulp in the sterilized containeris inoculated with a composite bacterial strain, and uniform mixing with the fruit pulp is carried out, wherein the weight amount of the composite bacterial strain accounts for 2 to 5% of the weightamount of the fruit pulp; fermentation filtering is carried out, an obtained biological insect trapping base material is mixed with sodium alkyl benzene sulfonate at a weight ratio of 200-400:1, and then an obtained product is canned. The fermentation process is simple and convenient; fermentation energy consumption is low; artificial labor intensity is saved; the method is suitable for large scale production; the biological insect trapping bait possesses obvious trapping killing effect on orchard common pests such as moth, chafer, and Apolygus lucorm, and is safe for natural enemy insects. In using process, the biological insect trapping bait is mixed with pesticides, an obtained mixture is introduced into an insect trapping device, and the insect trapping device is suspended on a tree, spraying is not needed, no influence on operators or the environment is caused, the biological insect trapping bait is safe, is friendly to the environment, and is especially suitable to be used for insect prevention and control in plantation of green agricultural products and organic agricultural products.