Does ace beat king in 7card stud?

In most games, yes. Many also allow it to be either above or below (e.g. in blackjack it can be worth 1 or 11, king is worth 10; in Poker it can be used above the king or below the 2).

However, some games fix the value of the ace as below the king. This is the same as seeing it as a 'one' card for those games.