This thesis investigated the developing method of matching reader to texts. This thesis focused on the Lexile Framework which was developed by MetaMetrics. After reviewing prior researches, this thesis presented three principles for developing of method of matching reader to texts. The method of matching reader to texts must be intended to 1) developing test of reading comprehesion and analysing item difficulty, and 2) using regression analysis, and 3) translating the scale. To do this, this thesis suggested using item response theory, regression analysis and absolute scale.