Objective: This study aimed to investigate the effect of adding oat flour on the characteristics of potato-oat compound dough and determine the appropriate ratio of oat flour and potato. Methods: Five different ratios of oat flour (15%, 20%, 25%, 30% and 35%) were selected and the color difference, microstructure, textural properties, rheological properties and pasting properties of the oat-potato composite dough were measured and sensory evaluation was carried out. Results: With the increase of oat flour, the color of compound dough gradually changed to red and dark. The internal microstructure of the composite dough was getting closer and closer, and hardness increased gradually; in the dynamic frequency scanning process, the elastic modulus and viscosity modulus of the compound dough with different addition amounts first increased, then decreased and then increased, and the loss factor first increased and then decreased. The initial gelatinization temperature, peak gelatinization temperature and end gelatinization temperature of compound dough decreased first and then increased. The sensory evaluation showed that the overall score of oat flour was higher than that of composite dough with other added amounts in the range of 20% ~ 25%, and it was more acceptable to consumers. Conclusion: The appropriate amount of oat flour to be added was between 20% and 25%.