In this study, we designed an effective user interface (UIs) for lock screens using facial expression recognition technology and two interface methods to develop an application that induces positive emotional flow in children. There is not enough study considering practical use of lock screen with special characteristics for different types of user such as children. After that, in order to understand its effectiveness, the whole process on the methodology timeline consisted of two phases. As a result of the survey, children preferred a lot of tasks on the lock screen whereas adults who were the control group preferred a lower task load and were more likely to use the face recognition lock screen than the children. Based on the characteristics of the derived children, we expect to develop effective applications by integrating the results of the research and specifying the functions.