Although the e-commerce of agro-food in mainland China started much later than that in America and European Union, the speed and potential of its growing shouldn't be underestimated. In recent years, increasing cyber citizens emerged in mainland China, who'd created huge needs for online transaction for all kinds of commodities ranging from daily commodities to foods to facilitate their daily lives. Meanwhile, various favorable policies from the governments had provided strong support for the development of e-business. Based on the theory of supply chain and information communication theory, the paper was focusing on the process of selection between two kinds of e-commercial modes for agricultural enterprises, i.e. O2O and B2C. Nowadays these modes with respective features had been widely applied among various companies in agricultural industry. In this paper, several intangible variables and observational variables were proposed to facilitate understanding of the numerical internal connections inside, so as to find out the main decisive factors during selection between O2O and B2C for companies in agricultural sector in mainland China.