A pull-up fitness exercise machine comprises a base for securing all components, an upright column fixed to the rear of the base, a top cantilever pivotally coupled to the top of upright column, a linking rope coupled to an end of the cantilever, and an elastic member driven by the other end of the linking rope for constantly pulling a rotary latching plate to rotate appropriately. A pull ring unit is installed at the other end of the cantilever and operated together with a pull string and a plurality of pulleys to provide an up and down displacement stroke for pulling the support plate. Moreover, a rotating rod assembly is pivotally coupled to the bottom of the upright column, and the other end of the rotating rod assembly is pivotally coupled to the support plate. An assisted pushing unit is interposed between the rotating rod assembly and the base and has an adjustable pushing force to provide an appropriate upward pushing force to the support plate. In addition, a linking hook lever is coaxially coupled to a first pivot point of the rotating rod assembly and configured to be corresponsive to a hook post of the rotary latching plate for constantly locking the rotating rod assembly and maintaining the support plate at a low static position. In this way, the pull ring unit can be pulled to perform an expected motion when the support plate bears a gravitational force, the cantilever is pulled downwardly, and the linking hook lever is released from a locked status relative to the rotary latching plate. When the external force of the pull ring unit disappears, the support plate is descended by the gravitational force to resume its original position and locked to a low static position automatically.
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