Objective to investigate the knowledge of advance directives in patients to receive cardiopulmonary bypass cardiac surgery under extracorporeal circulation and to analyze the influencing factors. Methods Totally, 172 patients to receive cardiopulmonary bypass cardiac surgery under extracorporeal circulation were involved in the study through convenience sampling and completed the general demographic questionnaire and the knowledge of advance directives questionnaire. Results Among the participants, 41.4% had heard of advance directives, and 60.5% were willing to accept the advance directives. According to the results of binary logistic regression analysis, the following independent factors influenced patients′ acceptance of advance directives:educational levels, the persons who made medical decision, the person who made the most weighted decision, giving up treatment due to irreversible disease conditions or advanced stage diseases, the cognition whether quality of life or length of survival matters, whether or not to have heard of advance directives, whether or not to have heard of living wills, whether or not to have heard of durable power of attorney (P＜0.01 for all）. Conclusion Patients to receive cardiopulmonary bypass cardiac surgery under extracorporeal circulation had poor knowledge of advance directives, but they were supportive of advance directives. Improving patients′ cognitive level of advance directives will help to promote their acceptance of advance directives.