The invention discloses an automatic judgement method and device of a fracture-cave type oil reservoir inter-well communication mode. The automatic judgement method includes the steps that maximum fluctuation change amplitude characteristic parameters of production data of producing wells within a period of time after water injection of a fracture-cave type oil reservoir are traversed and calculated on the basis of a sliding window; change degree characteristic parameters of production indexes, including water yield and oil production, of all the producing wells are quantified through a multifractal spectrum after water injection of the fracture-cave type oil reservoir; and the calculated maximum fluctuation change amplitude characteristic parameters of the production data and the change degree characteristic parameters of the oil production and the water yield are compared with preset threshold value ranges of all the parameters, and therefore the fracture-cave type oil reservoir inter-well communication mode is automatically judged to be one of inter-well fracture communication, inter-well cave communication and inter-well fracture-cave compound communication. By means of the automatic judgement method and device, automatic judgement of the inter-well communication mode is achieved for the first time, the recognition efficiency is effectively improved, and oil reservoir production can be guided.