BackgroundThe professional competence of clinical undergraduates is an important topic of research, and no effective instrument to measure this competence exists. We aimed to construct a scale for clinical undergraduates to evaluate their professional competence and associated determinants. MethodsWe developed the competence scale on the basis of four medical education standards (Global Minimum Essential Requirements [GMER], World Federation for Medical Education [WFME] standards, WHO standards, and Chinese standards) and a literature review. We used focus group discussions to complete the scale. We selected 288 undergraduates from two typical medical colleges in central and southeastern China by multistage sampling. We used factor analysis, correlation analysis, and internal consistency reliability to verify the validity and reliability of the scale. FindingsFactor analysis showed a scale consisting of eight dimensions with a total of 51 items. These dimensions were essential medical knowledge, public health or social science, essential clinical skills, advanced clinical skills, communication skills, advanced study skills, critical thinking and adaptation, and professionalism. Cronbach's α coefficients among the eight dimensions were over 0·800, with mean scores of 1·76 for essential medical knowledge, 1·38 for public health or social science, 1·92 for essential clinical skills, 1·54 for advanced clinical skills, 1·77 for communication skills, 1·25 for advanced study skills, 1·60 for critical thinking and adaptation, and 2·34 for professionalism. Clinical undergraduates whose academic grade was over average level had a higher score in the dimension of essential clinical knowledge than did students at or below average level. Women would like to report better professionalism than men. InterpretationThe competence scale was shown with good reliability and validity. Results of factor analysis indicated a further optimisation is needed to medical education standards. Professional competence of the respondents was relatively poor. This study could be a reference for policymakers to modify medical education standards for clinical undergraduates in China and other countries with similar settings. FundingHuazhong University of Science and Technology (2015119) and Hubei Provincial Department of Education (2015042).