A full/multi nonce range search or just a partial range search?
1) In a single nonce range (0~2^32-1), the miner find a nonce which meets the requirement of the valid share, so the miner exits the nonce search for this work and submit the nonce instantly, and then get another work from the pool.


It doesn't, because the fact that you found a valid share doesn't mean that there's not another nonce that creates a share.


  Actually, my question implies another question, for a fixed work(except for the nonce), is it possible that more than one nonce can be found to get a valid diff 1 share?


Between 0 and 2^32 shares/blocks will be found for every nonce range.