Semantic radical is an important component of phonogram, which indicates the meaning of the whole character. Semantic radical is also an important entry point for phonogram sublexical processing. Over years, researchers have semantic radical’s two important functions——the semantic and syntactic features in depth discussions. It was found that, in semantics, semantic radical can impact the extraction of Chinese characters’ category meaning, defined feature meaning and action verb meaning; in syntax, the survey found that 90 percent of semantic radicals have obvious syntactic tendency, semantic radical in Chinese noun and verb classification plays an important role. The present study improves semantic radical cognitive work in two aspects. First, previous research just focus on semantic radical’s one function (semantic or syntax), but the present study attempts to comprehensive explore the time course of the two function. Second, previous research used character priming paradigm, which couldn’t separate character’s or radical’s effect clearly, so the present study replace the character priming for semantic radical priming. In short, the present research uses radical priming paradigm to explore the time course of semantic radical’s semantic and syntax activation. The present study uses 2 (priming type) × 3 (character type) × 3 (SOA) mixed experiment design, priming type and SOA are between–subject variable, character type is within–subject variable. Priming type includes two kinds: radical priming and sign (***) priming; character type shows the semantic and syntax relation between character and its semantic radical, which includes three kinds, S+G+, S+G−, S−G+. S+G+ character type means the character and its semantic radical have similar meaning and the same syntax type, for example, in semantic, radical “讠” indicate something related to word or talking; in syntax, it means verb tendency, because more than 50% character including radical “讠” are verbs. So, under “讠” priming, “说” is S+G+ type,“语” is S+G– type, “让” is S−G+ type. SOA include 3types, 57 ms、157 ms and 314 ms. The experiment logic is: if the radical priming is valid, then there will be significant difference between radical priming and sign priming. Under this premise, we use S+G+ as control condition, and compare S−G+ and S+G− with control condition under different SOA, if reaction time is significant different between S−G+ and S+G+ or between S+G− and S+G+, it could be inferred that semantic radical’s semantic or syntax information was activated. Experiment result shows that: for the whole semantic radical, its semantic information is activating from soa57 to soa314, but its syntax information is not activated through the whole priming time. But further analysis shows there exists different result between character radical (the radical could be a character by its own, such as “ ”) and non character radical (the radical couldn’t be a character by its own, such as “讠”). For the non character radical, its semantic information just activated in soa157, and its syntax information didn’t activate through the whole priming time. For the character radical, its semantic information activated through the whole priming time, and syntax information also activated in soa 314. The result indicates that: character radical and non character radical have different mental representation and the semantic and syntax activation time course, which was determined by semantic radical’s function.