Abstract: The sensitivity studies of a main feedwater line rupture for Qinshan nuclearpower plant are performed with RETRAN-02/MOD 002. The studies place emph-asis on the primary to secondary heat transfer models of steam generator, breaksizes, credit taken for functioning of reactor trip and timing of auxiliary feedwatersupply to intact steam generator, A typical case of the main feedline rupturis analysed. This paper presents the main results of these studies.