The purpose of this study is to improve the problem of vibration which occurs in a running reciprocating compressor, by determining an optimal crankshaft counterweight and narrowing the movement trajectory of the crankshaft connecting rod mechanism. An analytical solution method is applied to satisfy the requirements for vibration reduction. Use of finite element software is to simulate the modality and deformation of crankshaft under various conditions of counterweight. Modal testing shows a difference of less than 6 % between the simulation and the experimental results. After the crankshaft counterweight is machined and installed, the new crankshaft is able to reduce compressor vibrations from 32 mm/s down to 15.8 mm/s and noise reduction of 3 dB. This study can provide information pertaining to the design process and assessment to any future new compressor designs.