This paper investigates some of dominant linguistic and social trends of China in the context of COVID-19, through a comprehensive analysis of vocabulary usage patterns on Weibo, the biggest SNS platform in China. First, we introduce generative and informatic features of Weibo to highlight its distinctive characteristics from other media. Next, based on the actual utterances of 516 million Weibo users, we examined the individual linguistic expressions and collective mentality of Chinese people under COVID-19. In detail, we established COVID-19 Weibo big data which consists of 136,585 Weibos of 22,985,364 characters, and gave a qualitative and quantitative analysis from four different functional perspectives - information seeking, emotional release, citizenship behavior and social connection. In this analysis, we clearly demonstrated some widespread linguistic and cultural phenomena, such as the spread process of Chinese naming for COVID-19 and ‘GuanZhuangBingDu’ being widely used, broad textual tendency to avoid negative emotional expressions and prefer conceptual metaphors, and common types of social connections through hashtags.