本研究旨在透過事件相關電位探討國小學童識字量與中文構字知識發展的關係。實驗刺激包含真字、假字(符合構字規則但不存在之部件組合)和非字(違反構字規則之筆劃部件)，分別請成人和國小學童進行讀音判斷作業，以N400做為詞彙觸接和語意整合之指標。成人的資料顯示假字誘發最大振幅的N400，真字次之，非字最小。國小學童則依據中文年級認字量表分數，分為高、中、低識字年級三組。中、低識字年級學童所展現的詞彙效應為非字最負，然後依序為假字與真字，此形態主要表現在前側電極位置。高識字年級組學童雖然在前側電極位置也展現相同的詞彙效應，但在後側頂葉的電極位置，則表現出如同成人的詞彙效應形態。整體而言，在發展過程中，學童的字彙辨識系統不同於精熟閱讀的成人，對於所有語言訊息採相對開放的處理方式，但隨著識字量的增加，對於合法構字的假字和違反構字規則的非字處理方式，可逐漸展現出類似於成熟讀者的趨勢，亦即對於部件層次的構字規則更為敏銳。 The present event-related potential (ERP) study aimed to investigate how reading ability shapes the development of Chinese orthographic knowledge in elementary school children. Participants were asked to make a pronounceable judgment when they viewed the stimuli which consisted of real-characters, pseudo-characters (a novel combination of semantic-phonetic radical with legal orthographic structure) and non-characters (illegal combination of strokes and radical position). The N400 was used to reflect the ease of lexical assess and semantic integration. In adults, pseudo-characters elicited the largest N400 amplitude, followed by real-characters and then non-characters. Children were divided into high-, medium- and low-reading grade groups based on their Chinese character recognition test scores. In medium- and low-reading grade groups showed a reverse pattern of the lexicality effect, which non-characters elicited more negative N400 than the pseudo- and real-characters did and the effect was mainly found in frontal electrodes. The children with high-reading ability also revealed the similar pattern in the frontal region, and exhibited an adult-like lexicality effect (pseudo-characters > real characters > non-characters) at the posterior electrodes. In sum, the present results suggests that the neurocognitive word-processing system in elementary school children is more open to all kind of linguistic possibilities than the word-processing system in skilled readers. However, as children’s character size grows, it would enhance children’s sensitivity for the orthographic constrains of Chinese radicals.