ObjectivesThis study aimed to determine the changing prevalence of five chronic non-communicable diseases (NCDs)- hypertension, coronary heart disease (CHD), stroke, chronic obstructive pulmonary disease (COPD), and asthma- and its multimorbidity (refers to the co-existence of two or more chronic diseases in an individual) across socioeconomic spectra in rural southwest China.MeasurementsTwo cross-sectional health interviews and examination surveys were conducted among individuals aged >= 35 years in rural China. An individual socioeconomic position (SEP) index was constructed using principal component analysis. Anthropometric measurements, blood pressure, and post-bronchodilator spirometry tests were recorded for each participant.ResultsThe mean age and proportion of men was 56.1 years and 48.4% in 2011, while was 56.6 years and 49.4% in 2021. From 2011 to 2021, the overall prevalence of hypertension, stroke and COPD increased from 26.1%, 1.1%, and 8.7% to 40.4%, 2.4%, and 12.8%, respectively (P < 0.01), while prevalence of CHD (2.1% vs. 2.2%) and asthma (1.4% vs. 1.5%) did not differ between the two study years (P > 0.05). The prevalence of NCDs multimorbidity increased from 2.3% to 9.7%, and was also observed among subgroups categorized by sex, age, ethnicity, level of education, income, and SEP (P < 0.01). In addition, the relative increases in the prevalence of multimorbidity were greater among men, old individuals, ethnic minorities, and those with low level of education and low SEP. Both in 2011 and 2021, ethnic minorities and individuals with lower level of education and low SEP had a higher prevalence of multimorbidity of the five studied chronic NCDs than their counterparts (P <0.01).ConclusionsThe prevalence of NCDs multimorbidity increased substantially across all socioeconomic gradients in rural southwest China. Future interventions to further manage NCDs and their multimorbidity must be tailored to address socioeconomic factors.