This study aims to develop a Measure of Taiwanese Children's Multiple Text Comprehension (Double MTC) and validate its effectiveness. Guided by the Construction-Integration Model and Multiple Document Model, four components of multiple-text comprehension were defined. A test suite consisting of six testlets, including 41 multiple-choice and 17 constructed-response items, was designed. These booklets covered a variety of text genres. The target participant pool was drawn from an extensive dual literacy project. The Double MTC was administered to 1,790 students in grades 3-6, using a non-equivalent groups design with anchor tests. Data were analyzed using a generalized item response model, yielding satisfactory Cronbach's alpha values for overall comprehension and its subdimensions, and acceptable item-model fit indices. In addition, correlations with established standardized tests demonstrated small to medium effect sizes, thus substantiating the criterion validity of Double MTC. Overall, the Double MTC appears to be an effective tool for assessing multiple-text reading comprehension among elementary school students.