Abstract: In order to explore the role of semantic radicals of Chinese characters in grammatical categorization of Chinese visual words, three experiments were conducted. Experiment 1 indicated that semantic radicals of Chinese characters provided important information of grammatical classes of words and played important role in categorization of Chinese nouns and verbs. When agreeing with the grammatical classes of the words, semantic radicals could promote the cognition of words’grammatical meaning. Otherwise, they would interfere the cognition. Experiment 2 showed that high frequency words were classified faster and with lower error rates than low frequency words. There were notable interaction between semantic radicals and word frequency, the effects of semantic radicals on categorization of low frequency words were more striking. Experiment 3 showed that the concreter the words were, the faster the words were classified, the lower error rates were produced. But there was no interaction between the role of the semantic radicals and word concreteness. The semantic radicals agreeing with the grammatical classes of words would progress both high concrete words and low concrete words. The whole study showed that semantic radicals of Chinese characters are processing units of both Chinese nouns and verbs. Semantic radicals are not only“structural chunks”and“semantic chunks”, but also“grammatical chunks”. This phenomenon are attributed to the structure characteristics of Chinese nouns and verbs. By semantic radicals, most of Chinese nouns mark the materials that things were made of or made from, and most of Chinese verbs mark the organs or tools of actions. The discovery of the grammatical meaning of semantic radicals will illuminate the teaching of Chinese. It also will enrich the theories of Chinese and the cognition of Chinese characters and words

Key words: semantic radicals, nouns, verbs, categorization