This paper incorporates both attribute and error pattern into the cognitive diagnostic model and takes two math topics, which were Fraction and Proportional Reasoning, as examples to construct the cognitive diagnostic assessments that would eventually evaluate students’ attribute and error pattern. As shown in the result, the reliability of “Fraction” and “Proportional Reasoning” are respectively 0.82 and 0.83. Also, this paper utilizes judgements from experts as criteria and the consistency between such criteria and the results of the cognitive diagnostic model for “Fration” and “Proportional Reasoning” is both about 0.85, indicating the cognitive diagnostic model could offer valid feedback to students as well as teachers and serve as guidance of remedial instruction.