Using the data of Chinese General Social Survey from 2010 to 2018, this study measured the modernity of Chinese peasants from four dimensions: equality and autonomy, positive attitude, general confidence, and open-mindedness. Hierarchical age–period–cohort models were introduced to assess the effect of age, period, and cohort on modernity and to further explore the heterogeneities in the effect of education and off-farm work experience on modernity among various birth cohorts. Age effects consistently show significance, with the level of individual modernity decreasing as age increases. However, the rate of decline gradually slows down. Period effects are generally significant and contribute to the advancement of modernity. Cohort effects are significant in most cohorts. The modernity of peasants born between 1941 and 1960 show a consistent decline, reaching its lowest point in the cohort 1961–1970 and then increasing steadily among those born after 1970. Possible explanations were proposed from the perspective of changes in the land property system and household registration system in China. We also found that the positive effect of education is stronger for younger cohorts, whereas the positive effect of off-farm experience is stronger for older cohorts. This study enriches Inkeles’s research on individual modernization and reveals the transformation process of traditional peasants in developing countries.