Machine utilizes dynamic balancing principle, through computer measurement control system to find out the central principal axis of inertia (normally called mass central axis) of the crankshaft roughcast and machine center holes on this axis. Mass centering machine can effectively reduce the initial imbalance of the crankshaft machined, thus improve the final balancing accuracy and efficiency of the crankshaft. Reducing initial imbalance is very important to crankshafts with balancing clump weight. Less imbalance means less mass reduced from the balancing clump weight during balancing and alignment, so as to guarantee the internal mass compensation in regard to structure design of the crankshaft.