Improving the quality of care relies on understanding patients' perceptions and expectations based on their experiences. The study aimed to determine the gaps between patients' perceived value and expected value, and to identify critical areas for outpatient service improvement.This cross-sectional study was conducted in China from November 2020 to February 2021. A sample of 572 outpatients, randomly selected from a comprehensive tertiary public hospital, was surveyed using a validated patient perceived value questionnaire. Importance-performance analysis was used to evaluate the differences between patients' perceived and expected value.The scores of patients' expected value for outpatient services were significantly higher than their perceived value in all 29 items and 8 dimensions. The items with the highest and lowest gaps were "short waiting time" (-1.52) and "hospital reputation and popularity" (-0.24) respectively, and the dimensions of price and efficiency (functional value) were located in the quadrant of high expectation and low perception.Our findings are useful for hospital administrators and policymakers to identify strategic focus areas and allocate resources rationally and effectively. We suggest healthcare providers should take measures to narrow the gaps, especially in terms of service efficiency and price.