The solar tracker is used to adjust the tilt angle of the solar panels automatically so that they are always perpendicular to the direction of the sunlight. To optimize the monitoring process for the parameters of the solar tracker system, the monitoring process needs to be carried out remotely and in real time through a mobile application. Based on this, the author tries to design an application for monitoring the solar tracker system. This application development uses a waterfall development model which consists of determining specifications, designing, implementing, and testing applications. The application development process uses the Flutter Software Development Kit (SDK) and Firebase as the database. User experience testing using a questionnaire with 32 respondents. The result of the implementation is an android-based application. This application has the main features for monitoring the parameters of current, voltage, energy, and power from solar panels and batteries. This application has a login feature. The application also has a power parameter graph and power parameter history list. The application also has user profile and about application features. This app can receive data from Firebase in realtime. The user experience test results are grouped into 6 categories, namely stimulation, attractiveness, novelty, efficiency, perspicuity, and dependability. Each rating for each category is 0.99, 1.43, 0.77, 1.23, 1.13, and 1.18 with a scale of -1 to 2.5. All features in the application can function properly. Then, the level of user experience is above average for the categories of dependability, efficiency, novelty, and attractiveness.