Question

I want let user mark their position in our google maps application and then save it to our database, then it can be showed in our google maps application in the next time.

Answer 1

If you want to save the position where the user clicked you can use a “click” listener to get the latitude and longitude of the click with code like this then send it to your server using an Ajax style call where it can be stored in the database.

var clickListener = GEvent.addListener(map,"click",
    function (overlay,latlng,overlaylatlng) {
        alert(latlng);
});

This code is for v2 of the Google Maps API. Version 3 should have something similar.