The invention discloses a safety margin risk quantification method. The risk value of the safety margin is quantified by acquiring the assets, threat, vulnerability and the existing safety protection measure information of the safety margin. The method comprises the following steps of: quantifying the asset value through the confidentiality, integrity and available evaluation value of specified assets in the safety margin; quantifying the asset damage possibility by acquiring an attack alarm event suffered by the assets in unit time, the asset vulnerability scanning result and the protection degree of the existing safety protection measures on the assets; calculating the risk quantification value of the assets through the asset value and damage possibility; and calculating the risk quantification value of the safety margin through the calculated risk quantification value of all the assets in the safety margin in the unit time. The system comprises an asset value definition module, a threat detection module, a vulnerability detection module, a safety protection measure definition module, an asset risk quantification module and a safety margin risk quantification module.