The invention discloses a manufacturing method of a polycrystalline silicon battery piece. The method includes the first step that a seed crystal layer is paved through seed crystal, and a polycrystalline silicon ingot is prepared through induced growth and directional solidification of the seed crystal layer, wherein crystal grains in the polycrystalline silicon ingot are formed through induced growth of seed crystals in the seed crystal layer; the second step that the polycrystalline silicon ingot is cut vertically and then cut horizontally to form polycrystalline silicon sheets, wherein the surface of each polycrystalline silicon sheet comprises crystal grain cross sections formed when the polycrystalline silicon ingot is cut horizontally; the third step that a plurality of mutually paralleled silver thin gates are printed on the surface of each polycrystalline silicon sheet in a battery gate line printing method; in the process of arranging the seed crystal layer in a paving mode, the seed crystals with long and narrow cross sections are fully or partially used to grow crystal grains which can generate long and narrow crystal grain cross sections. According to the method, the crystal grain cross sections and relative arrangement positions of the crystal grain cross sections and the gate lines are selected in an optimized mode, the polycrystalline silicon battery piece of which crystal boundaries are introduced moderately is manufactured, and therefore an electron can span the crystal boundaries as little as possible, and the density of the crystal boundaries can be controlled within a proper range; dislocation is absorbed through the crystal boundaries, the minority carrier lifetime is prolonged, and photoelectric conversion efficiency of a battery is improved.