Abstract: Objective To investigate the willingness-to-participate in medical insurance and its influencing factors among urban and rural residents.Methods Stratified random sampling was used to recruit 1 160 residents from 5 municipalities in Shandong province for a household face-to-face questionnaire survey on willingness and relevant factors for participating in medical insurance during September 2015.Chi-square test and logistic regression model were applied in data analyses.Results Of the residents,80.7% reported the willingness to participate in urban and rural medical insurance system and 19.3% did not report the willingness; 73.6% expressed their satisfaction about current medical insurance system while 13.7% were not satisfied with the system; 42.4% did not present the understanding to the current medical insurance system and only 26.3% showed the understanding to the system.The results of multivariate logistic regression revealed that main hindering factors for the willingness to participated in the medical insurance system included dissatisfaction to the system (odds ratioOR=2.967) and with poor understanding of the system (OR=2.332) and main promoting factors included the education level of high school (OR=0.336) or college and above (OR=0.325),with the annual family income of 10 000-24 999 RMB yuan (OR=0.578),25 000-39 999 (OR=0.473), ≥ 40 000 (OR=0.448),and residing in Zibo city (OR=0.454) or Jining city (OR=0.475) (all P<0.05).Conclusion Special attention should be paid to the need of medical insurance among the residents with various familial income and the systemic rationality of the integration of urban and rural medical insurance to promote the residents' willingness to participate in the medical insurance system.