The invention discloses a preparation method of the back side point contact of crystalline silicon. The preparation method comprises the following steps that 1, the monocrystalline silicon wafer surface is subjected to damaged layer removal, and in addition, the textured velvet structure is formed; 2, a velvet silicon wafer is inserted into a quartz boat for diffusion to form PN junctions, and a square resistor is formed at the front side of the silicon wafer; 3, the PN junctions at the periphery and the back side of the silicon wafer are removed, and meanwhile, HF (hydrogen fluoride) is adopted for carrying out roughness removal diffusion to form phosphorosilicate glass; 4, silicon nitride passivation antireflection coatings are respectively deposited at the front and back sides of the silicon wafer by a microwave method plasma chemical vapor deposition method, and in addition, points for point contact are preserved on the back side; and 5, a screen printing technology is adopted for sequentially printing a front side electrode, a back electric field and a back electrode of a battery, the back electrode is printed with silver paste, the back electric field is printed with aluminum paste, the front side electrode is printed with sliver paste, and in addition, good ohmic contact is formed through sintering. The preparation method has the advantages that silicon nitride films are plated on the front side and the back side of the silicon wafer, meanwhile, the points for point contact are preserved on the silicon nitride layer at the back side, the process is simple, and the manufacture cost is reduced.