With the CiteSpace software, visualized analysis of domestic register studies within ten years indicates that the key words "translation" and "ESP" of high frequency have been the focus. At present, the application of register theory to ESP teaching mainly concentrates on the demonstration of its guiding significance. Based on the register theory, the paper illustrates the embodiment of three variables—field, tenor, and mode—in the ESP textbook and explores the relationship of system and instance between three variables of register and the compilation of ESP textbooks. The study aims to provide a research perspective and the proof for compiling the ESP textbooks.