A method and device for controlling a DCDC converter, used for a hybrid electric vehicle and relating to the technical field of vehicle control. The method comprises: according to an output end current limit value and an actual voltage value, acquiring a first preset value corresponding to an input end power; according to the maximum discharge power of a high-voltage battery and the actual discharge power of an electric motor, acquiring a second preset value corresponding to the input end power; and determining the minimum value in the first preset value and the second preset value as an input end target power limit value. Multiple combination working conditions of sufficient or insufficient power sources at the input end are considered.