The invention discloses a latch device of a covering cap. The latch device comprises a lock shaft (4), at least one latch shaft (9), at least one latch unlocking mechanism (2) and at least one latch mechanism (3); the lock shaft (4) and the latch shafts (9) are separately arranged on the covering cap (1); each of the latch unlocking mechanisms (2) comprises a crankshaft (6) arranged on the lock shaft (4), a connecting rod (7), one end of which is hinged to the crankshaft (6) while the other end of which is rotatably connected to the latch shaft (9), and a latch (11) arranged on the each of thelatch shafts (9) and a latch slot (12) matched with the latch (11); the latch slot (12) is formed in a cap frame matched with the covering cap (1); and each latch lock mechanism (3) comprises a lock(5) arranged on the lock shaft (4) and a latch lock (10) arranged on each latch shaft (9). The latch device of the covering cap disclosed by the invention is simple in transmission relationship and small in occupied space, and can be applied to various covering caps.