The invention relates to a preparation method of a vitrified small ball, which comprises the following processing steps of surface softening, inner softening, crystal water gasifying, expanding without breaking shell, superficial vitrifying cell-closing, superficial cell-closing reinforcing, reinforcing again and obtaining the finished product. The vitrified small ball prepared by the technologyhas hard surface, high vacuum and no water sucking, thereby having the advantages of high strength, low thermal coefficient, and the like.