and one more question, when i upload some big zip file.
some time this process will be broken and system will re-upload auto.
in re-upload process, will the destination SFTP server have a broken zip file or not?
WinSCP wouldn't resume the transfer, if the result would not be a valid file. Of course the disconnect is an indication of some problem. So you never can be 100% sure. But there's just a small probability of a problem.