Objective This study aims to develop a training course syllabus in geriatric medicine for resident instructors to enhance their relevant knowledge. Methods From January 2024 to July 2025, 44 experts from various resident programs in 15 provinces were invited to participate in the study. Through literature review and expert interviews, an initial outline for a training course syllabus of geriatric medicine for resident instructors was developed. Three rounds of expert consultation using the Delphi method were conducted. The experts evaluated the importance of the course syllabus content and provided specific suggestions for modification. Quality control and statistical analysis were conducted using the expert positive coefficient, authority coefficient, group coordination coefficient, average score of questionnaire items, frequency of full scores, and coefficient of variation. Results The response rates of expert consultation were 100.0%, 94.4%, and 100.0%, indicating high levels of expert participation. The authority coefficients of the experts were 0.84, 0.88, and 0.97, suggesting strong reliability. The intra-group consistency coefficients were 0.98, 0.96, and 0.95, reflecting a high degree of consensus among the experts. The training course syllabus consists of three modules: basic knowledge of geriatric medicine, clinical characteristics, and teaching features. The mean importance scores of these modules ranged from 4.91 to 4.97, with a coefficient of variation ranging from 0.01 to 0.02. The three modules included 8 training components and 19 teaching items. The average importance values for the training components ranged from 4.69 to 5.00, with a coefficient of variation from 0.01 to 0.06. The average importance values of the teaching items ranged from 4.71 to 5.00, with a coefficient of variation from 0 to 0.05. Conclusions This study designed a training course syllabus for resident instructors to develop the concept of geriatric medicine. The course syllabus covers core knowledge and skills in geriatric medicine that demonstrate scientific validity and reliability, effectively meeting the need to promote geriatric medical concepts among resident instructors.