The invention particularly relates to a flexible self-adaptive clearance compensation lock mechanism and a use method thereof. The flexible self-adaptive clearance compensation lock mechanism is usedfor locking a large-scale airtight cabin door and can perform self-adaptive clearance compensation on an airtight cargo door of a large transporter and an ultra-large type airtight cabin door lock mechanism of a spacecraft. The prior art is inconvenient in clearance adjustment and needs manual adjustment of each pair of latch hook and lock bracket. A hydraulic system is added to a latch hook or alock bracket on a cabin door or a door frame. One/one pair of hydraulic piston section is arranged on each latch hook or lock bracket. All the piston sections constitute a communicating device. Pressure is supplied by the same hydraulic source to eliminate an assembly clearance between the latch hook and the lock bracket. The assembly difficulty is reduced. The lengths of the piston sections are formulated according to the demand on the assembly accuracy. The problems of troublesome adjustment procedure and difficult construction of a cooperation between the latch hook and the lock bracket, aswell as between a lock tongue and the lock bracket, in large-scale cargo door lock mechanisms of the transporter and the spacecraft are solved. Clearance compensation of the latch hooks and the lockbrackets of various ultra-large type airtight cabin doors is realized.