The invention provides a pressing mechanism and a product assembling device. The pressing mechanism comprises a pressing assembly and a pressing power part; the pressing assembly comprises a base, a pressing rod and an ejecting rod, the pressing rod comprises a connecting end and a pressing end, the ejecting rod is arranged on the base and can be driven by the pressing power part to ascend and descend relative to the base, when the ejecting rod ascends, the pressing end is ejected and pushed to rotate to the releasing position opened relative to the base, and when the ejecting rod descends, the pressing end rotates to the pressing position folded relative to the base. According to the pressing mechanism and the product assembling device, the pressing mechanism is arranged at the corresponding station, after products and auxiliary materials are fed, fixing is achieved through the pressing mechanism, and instant moving of the products and the auxiliary materials can be prevented; meanwhile, in the pressing mechanism, the ejecting rod is driven by the pressing power part to drive the pressing rod to be opened and closed relative to the base, fixing and releasing of the products and the auxiliary materials can be achieved, the full process is automatic, the efficiency is high, and stability and reliability are achieved.