Background This study aimed to uncover the changing prevalence of obesity and its association with hypertension across socioeconomic gradients in rural southwest China. Methods Data were collected from two cross-sectional health interviews and surveys from 2011 to 2021 among individuals aged >= 35 years in rural China. Each participant's height, weight, waist circumference, and blood pressure were measured. The overall prevalence of obesity, central obesity, and hypertension was directly standardized by age based on the total population of the two surveys. Multivariate logistic regression was used to analyze the association between obesity and prevalence of hypertension and an individual socioeconomic position (SEP) index was constructed using principal component analysis. Results From 2011 to 2021, the prevalence of obesity, central obesity, and hypertension increased substantially, from 5.9%, 50.2%, and 26.1-12.1%, 58.0%, and 40.4% (P < 0.01), respectively. These increasing rates existed in all subcategories, including sex, age, ethnicity, education, annual household income, access to medical services, and SEP (P < 0.05). In both 2011 and 2021, lower education level and poor access to medical services correlated with higher prevalence of central obesity, while higher SEP correlated with higher prevalence of obesity and central obesity (P < 0.01). Prevalence of obesity was higher in the Han ethnicity participants and individuals with poor access to medical services than in their counterparts (P < 0.01). Whereas the prevalence of central obesity was lower in Han participants than in ethnic minority participants in 2011 (P < 0.01), this trend reversed in 2021 (P < 0.01). A positive relationship between annual household income and prevalence of obesity and central obesity was only found in 2021 (P < 0.01). Obese and centrally obese participants were more likely to be hypertensive in both survey years (P < 0.01). Conclusions Future interventions to prevent and manage obesity in rural China should give increased attention to high income, less educated, poor access to medical services, and high SEP individuals. The implementation of these obesity interventions would also help reduce the prevalence of hypertension.