We study the D-term contribution for anomalous U(1) symmetries in type I
string models and derive general formula for the D-term contribution,
assuming that the dominant source of SUSY breaking is given by F-terms of the
dilaton, (overall) moduli or twisted moduli fields. On the basis of the
formula, we also point out that there are several different features from the
case in heterotic string models. The differences originate from the different
forms of K\"ahler potential between twisted moduli fields in type I string
models and the dilaton field in heterotic string models.Comment: 16 pages, latex, no figur
