BACKGROUND: High-quality primary care reduces premature mortality in the general population, but evidence for psychiatric patients in China is scarce. AIMS: To confirm excess mortality in patients with severe mental illness (SMI), and to examine the impact of community-based mental healthcare and other risk factors on their mortality. METHOD: We included 93 655 patients in 2012 and 100 706 in 2013 from the national mental health surveillance system in Sichuan, China to calculate the standardised mortality ratio (SMR). A total of 112 576 patients were followed up from 2009 to 2014 for model analyses. We used growth models to quantify the patterns of change for community management measures, high-risk behaviour, disease stability and medication adherence of patients over time, and then used multilevel proportional hazard models to examine the association between change patterns of management measures and mortality. RESULTS: The SMR was 6.44 (95% CI 4.94-8.26) in 2012 and 7.57 (95% CI 5.98-9.44) in 2013 among patients with SMI aged 15-34 years, and diminished with age. Unfavourable baseline socioeconomic status increased the hazard of death by 38-50%. Positive changes in high-risk behaviour, disease stability and medication adherence had a 54% (95% CI 47-60%), 69% (95% CI 63-73%) and 20% (4-33%) reduction in hazard of death, respectively, versus in those where these were unchanged. CONCLUSIONS: High excess mortality was confirmed among younger patients with SMI in Sichuan, China. Our findings on the relationships between community management and socioeconomic factors and mortality can inform community-based mental healthcare policies to reduce excess mortality among patients with SMI.