Objectives This study aimed to explore the connections between language skills (vocabulary, syntactic ability, expressive sentence pattern production) and reading fluency in elementary school students. Methods The research involved 51 children from grades 1 to 6 in elementary schools across Seoul, Gyeonggi, and Chungcheong. Various tools, such as the text reading fluency test, receptive vocabulary test, and syntatic comprehension test, were utilized. Additionally, tasks evaluating written and spoken expressive sentence patterns were carried out through a fill-in-the-blank test and a discourse completion task. Descriptive statistics were used to analyze performance across different grade levels (low, middle, and high), examining significant differences between the groups. Correlation analysis was used to examine the relationships between each variable, and multiple regression analysis was performed to identify the factors influencing reading fluency. Results The study revealed variations in reading fluency and language skills (vocabulary, syntactic ability, scores on written tasks assessing expressive sentence patterns, and the number of expressive sentence types in oral tasks) among different grades. Correlation analysis indicated that scores on written tasks assessing expressive sentence patterns, receptive vocabulary, and the number of expressive sentence types in spoken tasks were correlated with reading fluency. As a result of multiple regression analysis, the explanatory power of linguistic variables on reading fluency was 51.9%. Conclusions In this study, we identified linguistic variables that are correlated with reading fluency in school-age children. Specifically, we found that the ability to produce expressive sentences was correlated with reading fluency. The results of this study suggest new implications for future reading fluency interventions.