Background As part of the core outcome set (COS), the core traditional Chinese medicine (TCM) syndrome set can improve the consistency of syndrome efficacy evaluation outcomes in TCM clinical research. Previous studies proposed and empirically verified a method of developing core TCM syndrome sets based on complex syndromes under the disease-syndrome combination research model. However, this method is developed on the basis of syndrome types, which has the limitation that the finally included syndrome types are too single to adapt to the complexity of clinical syndromes. Therefore, it is urgent to optimize the existing development method to balance the complexity of clinical syndromes and methodological feasibility. Methods This study adopted qualitative research methods to obtain opinions from TCM clinicians and researchers on developing methods, efficacy evaluation criteria, and construction forms through expert steering committee meetings and semi-structured interviews. The sample size of semi-structured interviews was determined until data saturation was reached, and thematic analysis was used to analyze the transcription results. Results In the expert steering committee meeting, 60% (3/5) of the experts believed that developing in the form of syndrome elements was more operable; in the semi-structured interviews, 77.78% (7/9) of the experts supported developing in the form of syndrome elements, considering it convenient to use. Meanwhile, the research team added an expert semi-structured interview link in the development process, which complemented the cross-sectional survey used in previous studies to jointly improve the original list of TCM syndrome elements. Conclusion The method of developing core TCM syndrome sets based on syndrome elements formed in this study can consider clinical practice while improving the unity of TCM syndrome efficacy evaluation standards, which is helpful to promote the standardized development of TCM clinical research.