Children tracking system is a solution for parents to supervise their children remotely. The existing system provides a monitoring function that can report when the child enters and leaves the school bus. However, this system is not equipped with the function to report to the parents when the child leaves the bus at restricted areas, such as the mall. To implement such system a GPS with high accuracy is required. It will be a problem if a shopping mall and a school are neighbors and due to low accuracy the system gives false reports to the parent. Kalman filter can improve the accuracy of a GPS point. This paper presents a research that applies Kalman filter to the described children tracking system. Improvements are proved by comparing a system minus Kalman filter with a system that applies Kalman Filter. The result is Kalman filter improves the accuracy of the system as big as bla percent.