Abstract. Nowadays, smartphone has been shifted as a primary needs for majority of people. This trend is making people do activities on their smartphone such as exchange information, playing games, paying bills, discussing ideas, etc. In almost every smartphone, security features (i.e. password, pin, face unlock) are already built in which are intended to protect the data inside the smartphone. Nevertheless, those security features are not perfect and have flaws either technically or by human errors. This research aim to provide an application that uses people' facial expressions to improve the security of smartphone, namely Android. We implement face detection and expression recognition in this application as an improvement from the existing unlock screen, which is face unlock. The results that are achieved from this research is an unlock screen application on Android devices that utilizes people' facial expression changes to open their smartphone. This application can eliminates the technical errors from existing face unlock screen application which can be deceived by photos.