Abstract: According to China national needs of 2000 m depth downhole seismic observation, using the design idea of ‘Deconstruction and Refactoring’ and the design method of deep integration of enabling technology and seismic technology, we innovatively carry out: ① the overall design of downhole very broadband seismograph; ② the design typification of its sub-systems of electromagnetic compatibility, environmental adaptability, and reliability; ③ the design of its components structure, function, and shell. The testing and trial operation results show that the newly developed downhole very broadband seismograph fully meets the design indexes.