The invention provides environment-friendly biological fuel for boilers. The biological fuel comprises the following raw materials: 40-80 parts of a palm fruit extract, 2-8 parts of methanol, 2-8 parts of ethanol, 3-6 parts of oleic acid, 2-6 parts of polydimethylsiloxane, 1-3 parts of hexamethyl cyclotrisiloxane, 0.2-2.0 parts of dimethyl carbonate, 0.1-1.0 part of ethyl tertiary butyl ether, 1-3parts of a stabilizer, 0.2-0.6 part of a metal corrosion inhibitor and 1-4 parts of a phenolic antioxidant. The preparation method comprises the preparation of a palm fruit extract and the mixing ofthe materials. The biological fuel oil provided by the invention is low in production cost and high in fuel oil utilization rate, the anti-explosion performance and the oxidation resistance are good,the service life is long, and the environment friendliness is achieved. The extraction efficiency of the palm fruit extract is high, the preparation process of the biological fuel oil is simple, the raw materials are easy to mix, and the production cost is low, so that the biological fuel is suitable for large-scale production and is worthy of promotion.