Focused on Xixia dictionaries, this paper collects and arranges allographs of Tangut script. Its type can be divided into allographs with variant configurations and allographs with form-altered, among which there are more of the former and fewer of the latter. Most patterns of the variations are bidirectional and general. Not only does the formation of the allographs have an objective basis but is also influenced by certain subjective factors such as convenient writing, beautiful figure, and taboo.