Cognitive Diagnostic Assessment (CDA) can diagnose test takers’ knowledge states and sub-skill mastery patterns and offer fine-grained information in its diagnostic feedback. This paper briefly introduces the working mechanisms and procedures of CDA, and reviews the achievements of current studies on CDA. Finally it is pointed out that the difficulties encountered are far greater than the achievements. Future research efforts should go into developing cognitive diagnostic tests in a strict sense, elaborating methods of Q-matrix validation and empirically investigating whether diagnostic results actually remedy learners’ deficiencies and promote learning.