The invention provides a crank circular slider mechanism which comprises a crankshaft having at least one crank pin (1-3); at least one circular slider (3) with an eccentric hole (3-1) which fits over the crank pin (1-3) of the crankshaft; at least one reciprocating element (5) with circular slider -receiving hole (5-4), which receives the circular slider (3) in a rotatable manner, the amount of the element is equal to that of the circular slider; and at least one dynamic balance rotary block with an eccentric hole (4-1) which fits over the same one crank pin (1-3) of the crankshaft" the dynamic balance rotary block and the adjacent circular slider (3) are fixed together. By means of proper selection of mounting place and mass of the dynamic balance rotary block the mechanism can convert the reciprocating inertia of the reciprocating element into the rotation inertia so as to obtain the balance effect. The invention also provides a part for the crank circular slider mechanism and an internal combustion engine
