I labeled some folder and files with "nosync", How should I set the filter to ignore these folder and files. I tried many times but failed.
Synching Folders by Label:
The sync tool is "file based" and can't filter by properties of the parent folder at the moment. (You can filter files in and out by things like their full path, which can take the parent folders' names into account, but the label on a parent folder can't be used to decide if a file below it will be synced or not. This limitation only applies to Sync and not other things which use filters.)
Saying that, it would be possible to do this using a script column which adds a property to files which reflects whether any of their parent folders have a particular label. That is probably more work to set up than it is worth, however.
Syncing Files by Label:
Doing it for files is easy:
(This also works if the files are in sub-folders. As long as the labels are on the file themselves, not the parent folders.)
If it supports this will be more useful: label a folder, all subfolder and files it contains could be filtered.