The invention discloses a crank block variable connecting rod mechanism without clutches or brakes, comprising an upper connecting rod which is connected with a crankshaft and a lower connecting rod which is connected with a sliding block; the upper connecting rod and the lower connecting rod are connected with each other by a shaft pin through an external side plate. The crank block variable connecting rod mechanism is characterized in that a connecting rod conversion mechanism is arranged between the upper connecting rod and the shaft pin; the connecting rod conversion mechanism is a cylinder structure which is provided with small cotter piston. The crank block variable connecting rod mechanism realizes a working state and a non-working state by switching a state that the connecting rodmechanism is broken into two rods and a state that the connecting rod mechanism is combined as a rod, and replaces the original sleeve clutch and brake, thus carrying out the normal processing operation of the press under a state without the clutch and the brake; furthermore, the noise, energy loss and heating caused by the clutch braking are eliminated. The crank block variable connecting rod mechanism without clutches or brakes prompts the non-clutch process of the medium and small sized mechanical press.