The purpose of this thesis is to describe the behaviors that multinational corporations(MNCs) and small and medium-sized enterprises (SMEs) are taking for carrying outcorporate social responsibility (CSR) under the context of sustainable development.Besides, the factors which drive and influence the performance are further exploredand discussed.The thesis is to be analyzed by means of a literature review, qualitative case study,semi-structured interviews, within case study and cross case study.By adopting these methods, the thesis shows that both MNCs and SMEs are aware ofand actively shouldering CSR in spite of different contents and approaches. MNCs areable to integrate economic, environment and social values into CSR strategy whileSMEs focus more on economic values. Competitive pressures, social expectations andinternal governance system are the main drivers of MNCs. By contrast, owners’ desiregives rise to the performance of carrying out CSR strategy by SMEs.It is suggested that a new domain of CSR namely, political social responsibility isfound through the study. It demonstrates that MNCs with the state-owned nature haveparticular missions and responsibilities to serve the country and society, which is notcommon but exists in the world.