In this article, finite element analysis software ANSYS is applied on the analysis of moving parts, which are primary parts in natural gas compressor, such as crankshaft, connecting rod and piston rod, etc. The movement and stress of these parts are analyzed by ANSYS. Based on assumptions, finite models are established. Stress distribution, inflexibility distinction and modal distinction are obtained, which are useful for the design and optimization of primary parts in natural gas compressor, and provide reliable theoretical foundation.