To judge the quality of evidence for any study should be through a process of critical appraisal, apply appropriate critical appraisal tools, and judge with fairness and objectiveness. That is based on validity, reliability, and applicability from study results to appraise the truth and accuracy of study. The CASP (Critical Appraisal Skills Program) with 11 questions is commonly applied to appraise and judge the quality of evidence of randomized controlled trial. This article explains the quality of evidence based on the appraisal contents and consequence through an example of the randomized controlled trial on Chinese medicine nursing intervention. This would improve nurses to understand the application of the CASP tool, and further judge the quality of evidence.