The invention discloses a transient voltage monitoring device and method for a direct-current field of a high-voltage convertor station. The method comprises: an all-optic electric field sensor arranged at a direct-current field of a high-voltage convertor station is used for measuring a space electric field in real time, and a field data acquisition sending device carries out data acquisition and the data are stored into a cache unit; an analysis module of the field data acquisition sending device invokes cache data and carries out a real-time analysis on an electric field measurement result, and once an electric field measurement amplitude exceeds a set threshold value, the data are taken out of the cache unit and are sent to a wireless communication module; the wireless communication module of the field data acquisition sending device receives the triggered measurement data and then sends the data out; after an antenna of a wireless data receiving device of a control chamber receives the measurement data, the data are uploaded to a center station by an internal network; and the center station converts a transient electric field measurement result transmitted by the internal network into a transient voltage waveform. On the basis of the principle, a technical problem of accurate and secure monitoring of a transient voltage of a primary side of a direct-current field of a high-voltage convertor station is solved.