Objectives To investigate the period prevalence of complex wounds among the overall inpatients, and the impact of complex wounds on inpatient health expense and length of hospital stay (LOS). Design An observational study. Setting 6056 healthcare institutions across Sichuan province in China. Participants This study included 4 033 763 people admitted to healthcare institutions during 1 September 2018 and 31 December 2018. Results The point prevalence of complex wounds was 4.07 per 1000 among inpatients in Sichuan. The most common complex wounds were pressure ulcers (1.47 per 1000 among inpatients). Older, male, Han ethnic groups and retired people were most likely to suffer from complex wounds. The median LOS was longer for those with complex wounds as their main condition of treatment compared with all-cause admissions in Sichuan (12 days compared with 7 days; p<0.001). The median cost of care for people with complex wounds was higher than for admission for any cause (¥6500.18 compared with ¥3337.16; p<0.001). People with pressure ulcers had the longest LOS, while people with ulcers related to diabetes incurred the highest costs. Conclusions Complex wounds, especially pressure ulcers, are common in Sichuan province and their presence is associated with significantly longer lengths of hospital stay and higher medical costs. Additionally, this study only included admitted inpatients during the sampling time period, hence the prevalence of complex wounds may be underestimated. The high prevalence rate and heavy direct and indirect disease burden of complex wounds indicate that health policies for early detection and prevention of complex wounds in elders are urgently needed.