How can I save all contacts into google account?
If you want to "sync on demand only": Just enable sync at the time of demand for, say, 10 minutes while connected to your local Wifi -- and then disable it again. Enough time for the service to get its job done. You can do so in "Accounts &amp; Sync"1, after chosing your Google account:

 

If next to "Sync contacts" you see the same circular symbol as the screenshot2 shows next to Sync Google Reader, you probably do not even need to activate the permanent sync, but simply hit it for a one-time "sync on demand".