The invention discloses a biological carbon energy water-soluble fertilizer, relating to the technical field of fruit and vegetable planting cultivation. The fertilizer comprises the following raw materials by weight percent: 30%-60% of potassium fulvate, 5%-25% of biological organic carbon, 5%-25% of potassium dihydrogen phosphate, 4%-15% of potassium sulfate and 5%-25% of urea. A preparation method of the fertilizer comprises the steps of preparing the raw materials, grinding the urea, grinding potassium fulvate into powder, extracting biological organic carbon, uniformly mixing the materials, metering, packaging, and detecting to obtain a finished product of the fertilizer. Potassium fulvate and biological organic carbon are rich in carbon, hydrogen and oxygen and have strong adsorption functions, and carbon, hydrogen and oxygen are organically combined with nitrogen, phosphorus and potassium to form six nutritional elements required by plants, so that the utilization rate of various nutrients is greatly increased, the usage amount is low, and the effect is good. The fertilizer can be quickly adhered to soil when meeting water and is organically fused together with the soil, holes do not need to be dug and the fertilizer is applied along with the water when the base fertilizer is applied to fruits and vegetables, the nutrient loss is not easily caused, and the labor and effort are saved.