Based on the Petrochemical Industry, this paper put forward a decoupling model, and adopted LMDI (Log Mean Divisia Index) method to construct an influencing factor model of carbon dioxide emission, which explored the impacts of industry energy intensity, energy scale, energy efficiency and industrial structure on the carbon dioxide emissions from the Petrochemical Industry. The research indicates that Chinese Petrochemical Industry has gone through four stages: Strong negative decoupling (1999-2002), Expansive negative decoupling (2003-2007), Weak decoupling (2008-2009) and Strong decoupling (2010)，and has taken on low-carbon economical characteristics of"Strong decoupling".The result shows that energy intensity is a key factor influencing decoupling effect, while adjusting industrial structure has failed to show clear decoupling effect.