It is unavoidable that the growing number of private automobiles offers some potential threats to society. Children have frequently locked in cars alone due to parental irresponsibility, which can result in accidents. In light of these issues, a method based on face traits has been created to improve the safety of children's riding. This system is a child-safety technology that uses human face features to judge the personal safety of children stuck in a car after it has been parked. Face detection, age recognition are the two essential components of the method. This paper describes and explains in detail the entire process of developing a Safety warning system (SWS) for recognizing a person’s age and face. Face detection and recognition methods that have been used are described and explained as well as development steps used in the development of a Safety warning system. The software solution describes the details of using the OpenCV library not only to detect whether children are left alone in a car but also to send the signal to the handheld device and mobile application.