The confirmation of measurability is the basic theoretical hypothesis in educational and psychological measurement. All the time it is generally believed that the statements about testability from E.L.Thorndike and W.A.McCall formed the theoretical basis and fundament of the psychological and educational measurement. This article proposed that the idea about the confirmation of measurability from E.L.Thorndike and W.A.McCall is not enough as the psychological and educational measurement theory premise. It suggests that the confirmation of measurability include three aspects about the objective of the psychological and educational measurement: the existence of quality of the objective, the relative stability and variability of quantity, and the feasibility of measurement tools for the objective of the psychological and educational measurement. It suggested that it is indispensable to improve the theoretical premise of psychological and educational measurement.