The ability to summarize information is important for understanding and remembering texts. Lacks of this ability, readers are not able to engage in the process of deleting, generalizing, and integrating those propositions of a text (Kintsch & van Dijk, 1978) and fail to comprehend the text. The purposes of this study were to evaluate a new diagnostic tool of text comprehension and scrutinize the development of children’s summarization ability. Sixty 3rd and 6th graders were recruited from an elementary school in Chia-Yi, Taiwan. All participants were administered 3 different versions of expository passages, which were “deletion,” “generalization,” and “construction” and asked to summarize them, respectively. A free-recall measure and a comprehension test were given after each summarization task. The findings indicated that the performance of summarization task was highly correlated to the performance of recall measure and comprehension test. In addition, there was developmental difference on the summarization task.