Authors proposes the method about describing risk of information system security with probability,define risk intensity,and discussed the mathematical method for computing total probability of risk and individual probability of risk in network information system.

In this paper, the value at risk (VAR) method used in the fields of financial risk assessment is introduced, the risk factors, threat, vulnerability, and assets are analized, and a risk quantification model and the method of calculating VAR are proposed.

The proposed method described risk quantification method by identifying and quantifying the significance of assets and the criticality of threats from the behaviors of entities,and designed trust computation methods based on the quantified risk.

From the bounded rational viewpoint of decision-makers, behavioral finance theories are introduced into the risk optimization system of institutional investors, which are studied under multiple mental accounts.