The global pandemic of COVID-19 has fundamentally changed how people interact, especially with the introduction of technology-based measures that aim at curbing the spread of the virus. As the country that currently implements one of the tightest technology-based COVID prevention policy, China has protected its citizen with a prolonged peaceful time of zero case as well as a fast reaction to potential upsurging of the disease. However, such mobile-based technology does come with sacrifices, especially for senior citizens who find themselves difficult to adapt to modern technologies. In this study, we demonstrated the fact that most senior citizens find it difficult to use the health code apps called ''JKM'', to which they responded by cutting down on travel and reducing local commuting to locations where the verification of JKM is needed. Such compromise has physical and mental consequences and leads to inequalities in infrastructure, social isolation and self-sufficiency. As we illustrated in the paper, such decrease in life quality of senior citizens can be greatly reduced if improvements on the user interactions of the JKM can be implemented. To the best of our knowledge, we are the first systemic study of digital inequality due to mobile-based COVID prevention technologies for senior citizens in China. As similar technologies become widely adopted around the world, we wish to shed light on how widened digital inequality increasingly affects the life quality of senior citizens in the pandemic era.