The invention discloses a novel multi-main-grid battery piece and a photovoltaic module employing the same. The key innovation point is a main grid line structure which is in a bi-wire flat ellipticalcomposite shape, wherein a single main grid line is formed by the connection of a plurality of flat elliptical bi-wires, and the end point of each small flat ellipse is a welding reinforcing point, thereby improving the reliability. The battery piece employs a bi-wire composite main grid. When the grid line at one end is aged and broken, the grid line at the other end still collects a current normally, and the overall power generation capacity cannot be reduced. The main grid line has the specification of 0.4mm*0.4mm (width*height or thickness). Compared with a conventional solder strip, themain grid line is small in shading area, and the slurry consumed by the front of a battery is about 30%-50% less than the slurry consumed in the prior art. A single wire of the main grid line in the bi-wire flat elliptical composite shape employs a three-rhombus-column-shaped focusing solder strip. The light received by the surface of the main line is reflected to the surface of the battery piecethrough secondary reflection and a rhombus structure, thereby increasing the light incoming quantity and improving the efficiency.