Objective: The paper analyzes the impact of outpatient security level on residents' willingness, continuity, payment grade of participation in basic medical insurance. Methods: Based on the CHARLS data from2011to2018, the paper uses outpatient reimbursement ratio to measure the level of outpatient security, uses Probit model to explore the impact of outpatient security level on residents' basic medical insurance participation behavior. Results: The improvement of outpatient security level of basic medical insurance can significantly increase the participation rate of residents, reduce the interruption of insurance coverage, raise the grade of insurance payment, improve the quality of participation. At the same time, improving the level of outpatient security can reduce residents' adverse selection behavior, the impact of outpatient reimbursement ratio on participation rate is more significant among young people, those with better health conditions. Conclusion: The level of outpatient security can enhance residents' willingness to participate in insurance, improve the quality of participation. It is recommended to improve the level of outpatient security steadily, adjust the deductible line for outpatient reimbursement, increase the proportion of outpatient medical expense reimbursement, expand the scope of reimbursement. Also, we should promote the linkage mechanism between the payment standards of medical insurance, the level of economic, social development, as well as the per capita disposable income of residents, formulate more refined, differentiated payment policies