The invention discloses a preparation method of silicon spheres of spherical silicon solar cells. The preparation method comprises steps as follows: Step 1: P-type silicon crystal grains are placed into a crucible; Step 2: the crucible is heated to 1,420-1,450 DEG C, so that the P-type silicon crystal grains are molten; Step 3: the crucible is pressurized to 110-130 Kpa by the aid of argon; Step 4: a pressurized silicon crystal grain molten solution passes through a nozzle of the crucible to form silicon spheres; Step 5: the silicon spheres pass through the nozzle and then fall from a free falling tower to a soft aluminum plate at the bottom of the free falling tower, the soft aluminum plate receives the silicon spheres, and accordingly, the silicon spheres are prepared. The method has the benefits that according to the silicon spheres adopted by the spherical silicon solar cells, a molten silicon raw material drops directly, homogeneous nucleation is realized without impurity components, and polycrystalline silicon spheres with diameters being 0.9-1.1 mm are produced. With the adoption of the technology, silicon material waste caused by cutting and grinding production processes can be avoided, the material utilization rate is high, and the cost can be effectively reduced.