Food security closely relates to both the food quality and food quantity (Bruhn and Schutz 1999;Pinstrup-Andersen 2009;Nie and Chen 2014). Many factors determine the food security and there is much literature to address this issue. Firstly, some authors focus on the food security under natural conditions. For example, Tirado et al. (2010) remarked the relationship between climate change and food security. Hessen et al. (2002) identified the relationship between the grazer performance and food security. Secondly, some researchers capture the effects of the technology and management on the food security. For instance, Diagne et al. (2013) recently addressed the irrigate rice productivity on the food quality.Meanwhile, some papers analyse the food security in economics. Unnevehr et al. (2010) considered the food quality with the economic method. Brewster and Goldsmith (2007) investigated the effects of the laws on food quality by comparison of the U.K. and the U.S. Nie (2014) recently considered the corporate social responsibility (CSR) in the food industry. Hoffmann (2005) described the relationship between the ownership structure and the endogenous quality choice of the food industry. Traill (1997) examined the effects of the globalization on the supply and the quality for food industries. Chaddad and Mondelli (2013) identified that the specific strategies of firms have effects on the firms' performance in the food industry.However, the literature related to the food security seldom takes substitutability into consideration. As we know, there exists a high degree of product substitutability in the food industry, while food producers are always asymmetric. So, what are the effects of the asymmetric competition on the food security? How about the welfare implications of the competition in the food industry with product substitutability?To address the two issues mentioned above, we further develop food security in economics and focus on the food quality and quantity by employing a two-stage game theory model. In the first stage, firms commit the food quality. At the second stage, firms compete in the food quantity. In the analyses of the food industry, we resort to the classic model of Dixit (1979), Sheshinki (1976), Matsubayashi andYamada (2008), and, Berry andWaldfogel (2010), in which both the quality and the quantity are simultaneously considered for an industry. Moreover, we consider both the Cournot competition and Stackelberg competition, and we compare the equilibrium under the two situations.The findings of the research reveal that, under Cournot competition, there exists a U-shaped relationship between product substitutability and food quality, while firms benefit from lower production Abstract: Th e paper analyses the eff ects of asymmetric competition on food industry with product substitutability by establishing a two-stage dynamic game model. Th e equilibrium is captured under both the Cournot competition and Stackelberg competition. Firstly, under the Cournot competition, lower costs yield a higher qu...