I create a path in google earth and create the animation by google tour function. But I also would like to add the icon (such as arrow or car) moving along the path during the tour. Is there any simple way to achieve this?
The way to create an icon that moves along a path, and turns to face the direction it's currently moving, is to use a "KML Track". It's easy to create a Track from GPS data (gpx file or otherwise) via the GPS import tool in Google Earth Pro. Then you can add a custom icon if you wish. Once you have that track animating the way you want, you can add it to your Tour.