The invention discloses a folding and unfolding mechanism. The folding and unfolding mechanism is mounted between an upper panel and a lower panel which are hinged, and is used for folding and unfolding the upper panel and the lower panel, and for overturning for 0-180 degrees between the upper panel and the lower panel; wherein the folding and unfolding mechanism comprises a four-connecting-rod assembly, a pushrod assembly and an auxiliary connecting rod assembly; the auxiliary connecting rod assembly comprises a first auxiliary connecting rod and a second auxiliary connecting rod, wherein one end of the first auxiliary connecting rod is hinged to one end of the second auxiliary connecting rod; the other end of the first auxiliary connecting rod is hinged to the lower panel; and the other end of the second auxiliary connecting rod is fixedly connected with a fourth connecting rod. The invention provides a mechanism, mounted between an upper panel and a lower panel which are hinged together, for folding and unfolding the upper panel and the lower panel, and for overturning for 0-180 degrees between the upper panel and the lower panel.