The invention relates to the technical field of metal plastic processing, in particular to an indirect liquid forging device and a mold clamping mechanism. The mold closing rigidity of a mold can be improved, and the precision of a product is ensured. The indirect liquid forging device comprises a constraint frame and a mold closing constraint mechanism; the mold closing constraint mechanism comprises a fixing device and a connector, and a bilaterally-symmetrical connection mechanism is arranged between the fixing device and the connector; the connection rod mechanism comprises a swing rod anda connection rod which hinged to each other; the mold closing constraint mechanism comprises a limiting structure for stopping the connection rod and the swing rod from swinging inwards; and the swing end of the swing rod is provided with a convex part, the constraint frame is provided with a slide hole located in the outer side of the swing rod, when the connector is driven by a movable transverse beam to move downwards till mold closing is completed, the connector continues being pushed by the movable transverse beam so that the connection rod mechanism can swing outwards, and the convex part slides into the slide hole and is matched with the slide hole so as to push and support the connector, and mold clamping is achieved.