With growing interest in the quality of sleep, the mobile sleep application market in Korea and China is on the rise. As a result, the importance of application design is also increasing. This paper is intended to analyze and organize the characteristics, advantages and disadvantages of mobile sleep applications’ UI design in Korea and China to present future UI design direction. The top three download applications were selected for analysis by Google Play stores in South Korea and China. The common elements of the four preceding papers' UI design were analyzed to derive three elements which are color, icon, and layout. These three elements were applied to this paper by case analysis and comparative research were conducted focusing on the main interface of mobile sleep applications in Korea and China. The results of this study show that the UI design of Korean mobile sleep applications has rich in color and the icons were designed with simple lines, so the layout was in unified shape. However, disadvantage is that it lacks interaction and fun with users. UI design of Chinese mobile sleep application has very high color intensity, interesting icons and changing motions, so its layout has enhanced interaction with users. However. disadvantage is that the main and secondary contents of UI design were not clearly distinguished, making it difficult for users to understand or use them. Hopefully, mobile sleep applications should strengthen their UI designs to improve users' sleep quality in the future.