bstract: Taking children motor skill disorder as example, this essay analyses subjectivity, uncertainty, and velocity of diagnosis expert system data and illustrates the computing process of certainty factor and fuzzy evaluation of symptoms. Based on this, the author design and develop the diagnosis expert system for children’s motor skill disorder, including knowledge base, evidence base, inference engine and user interface. The essay is of good significance for both diagnosis expert system study and early diagnosis and early intervention of children’s motor skill disorder.