Mullion connecting piece

The utility model provides a mullion connecting piece which comprises a U-shaped connecting piece body with an opening end, an ejector pin inserted into the connecting piece body and a spring, and a transverse connecting hole is formed in the top end of the connecting piece body. Clamping jaws are fixedly arranged on the two sides of the opening end; the upper end of the ejector pin is located in the transverse connecting hole, and the bottom end of the ejector pin abuts against the opening end. The two ends of the spring are connected with the ejector pin and the connecting piece body respectively. During assembly, the screw is inserted into the transverse connecting hole to extrude the ejector pin so as to open the opening end of the connecting piece main body, so that the clamping jaw is tightly jointed with the notch of the window frame profile. When the mullion connecting piece is adjusted, after the screw is detached, the ejector pin moves upwards under the assistance of the compressed spring, so that t