Read picture books
For young children, parents can let their children know that death is "unable to breathe, eat, walk and talk" by reading picture books, or they can tell their children "the life process of leaves" to let them know the life process of human beings.
see a movie
For older children, parents can take their children to watch some warm-hearted movies to explain death from a scientific point of view, such as cell aging and slow metabolism, so that children can understand that death is a normal life process.