The invention discloses a generator hydrogen leakage test online calculation device and method. The device comprises data acquisition equipment corresponding to a generator, the data acquisition equipment is connected with the computer through an analog-to-digital conversion module. The computer is connected with a human-computer interaction module; the computer comprises a generator hydrogen leakage test on-line calculation module. The generator hydrogen leakage test online calculation module is used for substituting the received parameter data into a hydrogen leakage calculation formula to calculate the hydrogen leakage of the generator, and the parameter data comprises data transmitted from the analog-to-digital conversion module and parameter values input through the man-machine interaction module. Online automatic calculation can be achieved, manual participation can be reduced, time and labor are saved, data verification and processing are conducted on real-time collected data through a data automatic collection technology and a large number of data calculation and analysis means, and the hydrogen leakage grade of the generator can be accurately evaluated online.