How can offline flash jetson TX1 system?
Not sure what you mean by “offline”. Flash is always via recovery mode over the micro-B USB with the host PC controlling the flash. Are you looking for something different?
Perhaps @sensor_test means without an active connection to the Internet like JetPack requires. You can either have JetPack download the packages ahead of time, or you can manually download L4T from a machine that does have a connection and copy it to your flashing PC.