Purpose: As a representative form of discourse, oral narratives offer a sensitive, flexible, and ecologically valid tool for language evaluation. Nevertheless, oral narrative assessments in mainland China remain uncommon among school-age children. Therefore, this study explores the effectiveness of narrative microstructural assessment in Mandarin-speaking school-age children. Its primary purpose is to lay a foundation for future clinical applications by establishing a feasible administration procedure and validating various viable measures to facilitate the evaluation of language proficiencies. Method: Narrative samples were collected through a single wordless picture from 285 Mandarin-speaking children ages 7-12 years (Grades 1-6). The samples were then coded using a semiautomatic method for 22 individual measures at word, sentence, and discourse levels. Results: The adapted elicitation method was effective for all grades, with most of the children's stories exhibiting sufficient length, coherent structure, and certain self-fabricated specifics. The semiautomatic coding was also convenient and promising. Altogether, 19 measures were identified as robust predictors of grades, revealing a general tendency of grade-related increase from Grades 1 to 5. These measures exhibited three representative nonlinear trajectory patterns with varied rates of increase. Then, we developed a comprehensive composite measure through factor analysis, which combined six individual measures. The analysis verified the single factor of narrative microstructural competence and showed strong evidence of construct validity. Conclusions: This study has provided a practical set of administration procedures, validated the efficacy of 19 individual measures as well as a composite measure, and offered corresponding field test data for clinical matching. The findings underscored the reliability and informative nature of oral narrative microstructural assessment in Mandarin-speaking school-age children.