When observing the WWD-0.8/10 air compressor that was noiseless and oilless, its vibration and noise were large. These phenomena were related to air compressors reciprocating inertial force and overturning moment which were separately depended on pistons acceleration and forces of connecting rod. Movement mechanisms three-dimensional solid model establishment, virtual assembly and motion simulation were accomplished by Pro/E. The main procedures were introduced in the paper. Many important metrical data obtained about pistons acceleration and forces of connecting rod by motion simulation could supply necessary references for air compressors dynamic optimizations.