The invention provides a method for calculating a disaster recovery point objective of an information system. The key of the method is an information system consisting of m production systems, wherein k items of services K1, K2,..., Kk run on the information system, and each item of service only can run on one production system. Through analyzing the importance of each production system, the importance of each service, the existing data volume and the data volume (per second) generated by each department in the information system, and based on the generated data volume (per second) relevant to each service, according to the percentage of the existing data volume in a service used by a department to the total data volume of the department, new generated data (per second) of each service and new generated data (per second) of the production system relevant to each service are estimated; and then, through synthesizing the importance of each production system in the information system, the generated data volume of a production system is divided by the newly increased weighted data volume of the production system so as to obtain a value of the disaster RPO (recovery point objective) of the whole information system.