A micro-carbon bio-fertilizer for rapidly increasing a soil granular structure and a preparation method thereof are provided. The formula composition of the micro-carbon bio-fertilizer by mass percentage is: 30-60% of micro carbons, and 40-70% of plant fibers. The preparation process includes is that: preparation of raw materials; filtration and purification of the raw materials; biodegradation; canning of semi-finished product; dispensing and mixing; sedimentation and achievement of finished product. The macromolecular carbohydrates contained in the industrial wastewater rich in organic matters are activated into micro carbons of 100 μm in average through biotechnologies. The micro carbons have natural affinity with soil and split the soil into small particles which are gathered to form a granular structure. Such a granular structure mitigates the degree of soil hardening and acidification, while quickly increasing soil fertility and improving crop quality and yield.
