  It is pointed out that finite-size effect is not negligible in locating
critical point of QCD phase transition at current relativistic heavy ion
collisions. Finite-size behavior near critical point, in particular,
finite-size scaling and fixed-point behavior of the final observables can be
served as a quantitative identification of critical point and the nearby
boundary of the QCD phase transition. The validity of the method at finite
detector acceptances at RHIC is discussed.
