A clamping unit for depositing a thin film solar cell and a signal feed-in method are provided. The clamping unit comprises an electrode plate module, a signal feed-in module (201), and a supporting frame. The electrode plate module is set with a shielding cover (204). The signal feed-in module (201) comprises a waist section and a head section, wherein the head section is a rectangular-shaped signal feed-in surface. The head section of the signal feed-in module (201) is surface contacted with and is connected to the feed-in port of the electrode plate module. The feed-in port is set on the concave rectangular surface which is arranged in the central region of the back side of the cathode plate of the electrode plate module. The clamping unit can effectively remove standing wave effect and skin effect, improve the yields and reduce the costs.