Abstract: CGN deterministic statistic methodology (GSM) is a loss of coolant accident (LOCA) analysis method that is between the most conservative evaluation model and the best estimate evaluation model. This methodology maintains the deterministic realistic method (DRM) penalization model to ensure the conservatism of the code models and penalizing assumption to ensure a conservative plant modeling, while applying random sampling technique to statistically quantify the uncertainty range and distribution of plant status parameters, and both parametric and non-parametric methods are adopted to calculate the statistical upper bounding value (PCT95/95). When applying the GSM for CPR1000 nuclear power plant LB LOCA analysis, the margin generated can be 9% compared with DRM conservative LOCA analysis.