What is the meaning of the mickey sword in Kingdom Hearts

I think you mean why does Mickey have one?
Sorry if I'm guessing wrong, it was just kind of unclear to me.

If that was what you were asking; here's the answer.

The keyblade is named The Realm of Darkness
King Mickey acquired this keyblade while stumbling through Kingdom Hearts. This key is identical to Sora's, except the blade is gold and the handle silver. It possesses all the power and authority of its twin, but its purpose is far different. Mickey must use this key to seal Kingdom Hearts, because two hearts and two keys are needed to close the Door to Darkness.

It is unknown by what means Mickey found or received the Keyblade, but some people think the fact that his silhouette appears in its keychain must have some deeper meaning.