The precise measurement to risks is principal for the effective risk management,both major in theory and practice.Value-at-Risk,a widely accepted risk measure,has some deadly deficiencies.The authors introduce a new risk measure,Conditional-Value-at-Risk,which comes into being based on the VaR measure. They introduce CVaR's definition and the risk-measuring model on it and also its applications in portfolio management,comparatively with VaR measure.