Objective To explore the factors associated with free medication compliance in communitybased patients with severe mental disorders at home in Huairou District of Beijing. Methods A total of 600 patients with severe mental disorders who were registered in the Beijing Huairou Mental Health Management System from March 2018 to March 2019 were selected by simple random sampling method， and investigated by Morisky Adherence Questionnaire （MAQ-8）. According to the results of the survey， patients were divided into poor compliance group （MAQ-8 score less than 6） and good compliance gourp （MAQ-8 score between 6 and 8）. The general characteristics （gender， age， working condition， living environment， marital status， living style， physical disease， family history， history of drug allergy， disease type， family income， education attainment， hospitalization times， etc.） and the factors influencing medication compliance were collected. 15 patients with severe mental disorders were interviewed， and the data were analyzed by phenomenological analysis. 9 themes affecting medication compliance were identified. T-test and Chi-square test were used to analyze the differences of general characteristics between the poor compliance group and the good compliance group. Multivariate logistic regression analysis was used to analyze the factors influencing the compliance. Results In this study， a total of 600 cases were screened and 435 cases of effective information were collected， among which 325 cases （74.7%） had good medication compliance and 110 cases （25.3%） had poor medication compliance. Among the reasons for not taking prescribed medication， the highest choice rate was forgetting to take medicine （60.0%， 66/110）， followed by lack of supervision （43.6%， 48/110） and lack of insight of the disease （35.5%，39/110）. Multivariate logistic regression analysis showed that the medication compliance of patients living in plain area was worse than that of patients living in mountainous area （OR=2.41， 95%CI：1.14-5.10，P ＜ 0.05）； the medication compliance of patients with monthly family income less than 3000 yuan was better than that of patients with monthly family income more than 5 000 yuan （OR=0.36，95%CI： 0.19-0.70，P ＜ 0.01）； low education level was a risk factor for medication compliance （OR=13.81，95%CI：2.82-67.7，P ＜ 0.01）. Conclusions Among the patients with severe mental disorders taking free medication in the community in Huairou District of Beijing， living environment， monthly household income， and education attainment are the main influencing factors of compliance. The reasons for not taking medication as prescribed include forgetting to take medication for various reasons， not taking medication without supervision of a guardian and lack of insight.