The working environment and influencing factors for working stability of typical press mechanical system was analyzed and summarized based on printing quality. The evaluation method of influence degree of factors for working stability was put forward based on broad sense definition of quality. Model J2108 offset printer was studied as sample. The results showed that roller vibration is the key factor for working stability; transmission un-stability and work part movement are the main and secondary factor. The purpose was to provide references to control printing quality and working stability control of printer in actual production.