It looks like a cheap knock-off of a Marto Excalibur...
If it is, there's a round 'button' at the end of the pommel. This is the nut that holds the whole thing together on the tang of the blade. If it's loose, take it apart and check for cracks, etc. - then, put the pieces back together and, wrapping the nut with a piece of leather or something to protect the finish, tighten it down with a pair of pliers.
If what I've just described doesn't appear to be familiar to your sword, then I might be incorrect.