Objective:To investigate secondhand smoke (SHS) exposure among non-current smokers aged 15 and over and its influencing factors in China in 2010 and 2018.Methods:The 2010 and 2018 China Adult Tobacco Surveys used multistage stratified cluster random sampling methods to obtain national representative samples across 31 provinces (autonomous regions and municipalities) in China. This study selected non-current smokers aged 15 and over as the research subjects to describe the general demographic characteristics, perceptions of SHS hazards, attitudes towards smoking bans in indoor areas in public places, and SHS exposure and the smoking restriction regulations in different places. The Rao-Scott χ2 test was used to compare the rates, and the unconditional logistic regression was used to analyze the influencing factors of SHS exposure. All the subjects in the analysis were weighted based on a complex sampling design. Results:Among non-current smokers aged 15 and over, from 2010 to 2018, the percentage of indoor smokers had decreased from 84.7% to 71.9%. The rates of people who saw smoking in various places declined with a statistically significant difference ( P<0.001). The exposure to SHS for females, people aged 45-64, teachers, medical staff, workers in enterprises, businesses, waiters, and people who live in rural and central areas declined. The differences were statistically significant ( P<0.05). In 2018, the percentage of SHS exposure for those who reported a comprehensive smoking ban in households or allowed smoking in certain areas was lower than for those who reported allowed or without a smoking ban. Among those aged 25-44, SHS exposure for those who reported complete smoking prohibition in workplaces was lower than those who reported allowed or without smoking prohibition ( OR=0.65, 95% CI: 0.49-0.87). The proportion of SHS exposure for those who believe that smoking should not be allowed in indoor areas of 0-5 public places is higher than that smoking should not be allowed in the indoor spaces of 8 public places ( OR=2.13, 95% CI: 1.35-3.36). Among people aged 45-64, the proportions of SHS exposure for teachers ( OR=0.37, 95% CI: 0.17-0.78) and medical staff ( OR=0.35, 95% CI: 0.16-0.76) and staff working in agriculture, forestry, animal husbandry, fishery, and water conservancy were lower than governmental staff ( OR=0.49, 95% CI: 0.29-0.84). Conclusions:Data from the decreased exposure of Chinese non-current smokers aged 15 and over to SHS suggests the initial achievement through constructing a smoke-free environment, but continued efforts are needed. It is necessary to actively advocate for smoke-free families, strengthen publicity and education on the hazards of tobacco and SHS, and improve the skills of non-smokers in rejecting SHS exposure.