The work aims to design a packaging machine suitable for multi-specification shallow egg tart cartons, in order to adapt to the automatic packaging of multi-specification shallow cartons. Based on the folding process of the shallow cartons, the folding trajectory of the flap, side plate and cover plate of the carton was equivalent to the movement model of each panel rotating along the fold, so as to design a tongue-inserting packaging machine which could adapt to different specifications of shallow carton packaging. With 5R mechanism of coaxial layout as the folding device of cover plate, its trajectory diversity and motion controllability were used to control its end output trajectory, thus achieving the folding and tongue insertion of the flaps, side plates and cover plates of the two-grain, three-grain, four-grain and six-grain egg tart cartons. The effective workspace of the prototype was 300 mm×200 mm×50 mm. It could fold and insert tongues for shallow cartons with outline dimensions ranging from 145 mm×78 mm×35 mm to 230 mm×152 mm×37 mm. The folding time of each carton was about 15 s. It can complete the packaging of various specifications of egg tart cartons and realize the automatic folding and packaging of shallow cartons. Featured by small space occupation and controllable movement, the proposed packaging machine can quickly adapt to the requirements of mass customized products.