Background: Little is known about the categorization ability of children with intellectual disabilities (ID) in China, which is critical in guiding teaching practice and learning support strategies for those students. The study has aimed to explore the characteristics of categorization ability of children with ID. Method: This study used an experimental method to compare the classification ability of children with moderate ID (n = 40, average age of 10.6, average IQ = 47.03), typically developing children of the same age (n = 40, average age of 10.5), and kindergarten middle-class children (n = 20, average age of 6.2) to find differences in categorization abilities, including selecting items in the same category, excluding items from a different category, and direct classification. Findings: We found that the classification capacity of 10-year-old children with moderate ID was significantly lower than that of typically developing children of the same age. There was no significant difference in the total classification score between 10-year-old children with moderate ID and 6-year-old typically developing children, while there were differences in the task of direct classification. Besides, there was a significant positive correlation between IQ and classification capability in children with moderate ID. Conclusion: Educators should develop corresponding educational programs based on the cognitive level and categorization ability characteristics of children with moderate ID.