In the study of phonetic characters, whether the lexical grammatical information can be independently activated through speech comprehension or production has been a controversial topic. In recent years, increasing evidence has shown that grammar exists independently from semantics and phonetics. Chinese characters are the only ideograms in the world. Chinese do not emphasize the grammatical categories of words, like phonetic characters, because Chinese words can represent a variety of word classes without changing the pronunciation and orthography. The complicated grammatical features of Chinese words make them difficult to be explored, but they still arouse researchers’ interest. Researchers have examined the grammatical activation of Chinese from the perspectives of sentence context, idioms, phrases, and Chinese words. Previous studies have also examined the grammatical features of Chinese words at or beyond the level of words. Accordingly, the present research extended the previous studies through the sub-lexical pathway. Semantic radicals are the ideographic components and concentrated embodiment of Chinese characters. Relevant statistics and studies have shown that semantic radicals also represent grammar. On the basis of these studies, the present work used the semantic radical priming paradigm to investigate the grammatical activation and related influencing factors of Chinese words from the sub-lexical processing level. Experiment 1 includes two small experiments, which examined whether the activation of the semantic radical’s grammatical information under the radical priming paradigm was specific to the task. Experiments 1 a and 1 b adopted a 2(semantic radical priming/control priming) × 2(G+ Chinese characters/G-Chinese characters) two-factor within-subject design. Experiment 1 a used lexical decision as the reaction task, whereas Experiment 1 b replaced it with grammatical classification. The comparison of results indicate that under the grammatical classification task, the grammatical information of semantic radicals was easier to activate. The discovery also set the foundation for the selection of the reaction tasks for Experiment 2. Experiment 2 further investigated the influence of family size and grammatical consistency on the activation of the semantic radical’s grammatical information. Experiment 2 a adopted a 2(large family size/small family size) × 2(G+ Chinese characters/G-Chinese characters) two-factor within-subject design to examine the influence of family size on the syntax activation of semantic radicals. The results of this experiment discovered the advantages of a big family. Experiment 2 b replaced the family size factor with grammatical consistency, and the results also revealed the advantages of high grammatical consistency. The overall results show that grammatical information can be activated at the sub-lexical level of Chinese words and the semantic radical marks the grammatical information. However, the activation of the semantic radical’s grammatical information is specific to the task. When the task is directly targeted to the grammar of the characters, the grammatical information can be easily activated. Family size and grammatical consistency are important factors that affect the activation of the semantic radical’s grammatical information. The results further manifest the promotion effect of a large family size and high grammatical consistency.