  Let $f:X\to Y$ be a surjective morphism of integral schemes. Then $X$ is said
to be quasi-galois closed over $Y$ by $f$ if $X$ has a unique conjugate over
$Y$ in an algebraically closed field. Such a notion has been applied to the
computation of \'etale fundamental groups.
  In this paper we will use affine coverings with values in a fixed field to
discuss quasi-galois closed and then give a sufficient and essential condition
for quasi-galois closed. Here, we will avoid using affine structures on a
scheme since their definition looks copious and fussy.
