Abstract: The steam generator overfilling of CAP1000 nuclear power plant in steam generator tube rupture （SGTR） accident was analyzed. The power range for this analysis included typical part-power, zero power and hot standby. The sensitivity analyses were compared at each power level. And the conservative case at every power level was selected to contrast with the result of full power. Based on the transient characteristics, the accident processes were analyzed, and then the limiting case and critical parameters were evaluated. It turns out that the steam generator of CAP1000 will not be overfilled in SGTR accident which is assumed to occur in entire power range, and the most limiting case appears in full power condition.