Objective: The paper compared the utilization characteristics and trends of the high-value drugs between hospital outpatients (in-hospital) and retail pharmacies (out-of-hospital) under the “dual-channel” policy, and empirically analyzed the factors influencing patients' out-of-hospital medication behavior of high-value drugs at the individual level. Methods: We collected medical insurance reimbursement records of all insured patients in Weihai City, Shandong Province from 2019 to 2023 and relevant policy documents. Patients who had utilized and reimbursed the high-value drugs within the five years were selected as study samples. Descriptive statistical analysis was used to compare the differences in the number of patients, visits, and costs between the two channels (in-hospital and out-of-hospital) and across the five civil years. The Heckman sample selection model was employed to quantify hospital medication behavior from two aspects: the probability of out-of-hospital drug procurement and the proportion of out-of-hospital medication, and identify the influencing factors of out-of-hospital medication behavior from the dimensions of individual characteristics, disease characteristics, and treatment characteristics. Results: From 2019 to 2023, the average annual growth of the number of patients, visits, and costs for high-value drugs in Weihai City was 47.67%, 78.72%, and 24.89%, in which out-of-hospital channel increased by 81.95%, 135.77%, and 63.57% and the corresponding proportion reached 87.41%, 88.60%, and 88.05% by 2023. The results of Heckman model showed that compared to 2019, the out-of-hospital medication behavior for high-value drugs became more prominent from 2020 to 2023 (P<0.01). The probability of out-of-hospital drug procurement has significantly increased by 82.5%, 149.5%, 179.7%, and 169.9% in the past four years. Conclusions: The “dual-channel” policy promotes a rapid utilization increase of the high-value drugs, with a prominent trend of prescription outflow. Patients' out-of-hospital medication behavior has significant age trends, and is driven by factors such as cancer, heavy medication burden, long medication cycles, and low frequency of in-hospital medication.