Objective To develop a scale for assessment of clinical competence of undergraduate nursing students and to test its reliability and validity, thus to provide effective assessment tool for nursing educators. Methods Using the practical competence theory as theoretical framework, literature review, semi-structured interview, and Delphi expert consultation were conducted to form the initial scale, then 100 undergraduate nursing students during clinical practice in a tertiary hospital in Shandong province were selected using convenience sampling and completed the scale. Items were selected through such statistics as t test, Pearson′s correlation coefficient and exploratory factor analysis. At last, 1 715 undergraduate nursing students practicing in 12 comprehensive ter-tiary hospitals in Shandong province filled out the scale to test the reliability and validity. Results 〖JP+1〗The final version of the scale included 44 items that assess seven dimensions of clinical competence: clinical nursing, communication and coordination, health education, scientific research and innovation, emergency cooperation, humanistic care and clinical teaching, which could explain 82.547% of the total variance. The total Cronbach′s alpha coefficient was 0.923 and the split-half reliability was 0.847. The content validity index for the scale was 0.895 and for each item ranged from 0.850 to 1.000. The correlation coefficients between dimensions and the total scale were 0.859-0.921，and those among dimensions ranged from 0.651 to 0.879. Conclusion The clinical competence scale for undergraduate nursing students has good validity and reliability for clinical use.