The invention provides a method and a device for reconstructing palaeo geomorphology in a hydrocarbon generation critical period. The method comprises leveling a palaeo geomorphologic top boundary formation to a preset time value, and determining a palaeo geomorphologic bottom boundary formation formed during palaeo geomorphic erosion and denudation periods using a sequence stratigraphic analysismethod according to well-logging data, instantaneous phase seismic attributes, and amplitude reflection characteristics of seismic sections; performing formation leveling on the palaeo geomorphologictop boundary formation to obtain the structural feature of the palaeo geomorphologic bottom boundary formation formed during the terminal stage of filling and completion of the palaeo geomorphology; and obtaining the structural feature of the palaeo geomorphologic bottom boundary formation formed during the hydrocarbon generation critical period according to the structural feature of the palaeo geomorphologic top boundary formation formed during the hydrocarbon generation critical period and the structural feature of the palaeo geomorphologic bottom boundary formation formed during the terminal stage of filling and completion of the palaeo geomorphology. According to the invention, the method and the device for reconstructing the palaeo geomorphology in the hydrocarbon generation criticalperiod provided by the invention are high in precision, easy to operation, and does not need to perform compaction correction.