The invention provides a testing device and a testing method for direct current porcelain insulator cap corrosion mechanism research. The testing device includes a direct current constant flow source (1), an electric current measurement device (2), an electrolytic bath (3), an insulating support (4) and a control monitoring system (5), wherein a zinc piece and an iron piece are suspended on the insulating support (4); the lower ends of the zinc piece and the iron piece are immersed in electrolyte of the electrolytic bath (3); the anode of the direct current constant flow source (1) is connected with the zinc piece and the iron piece, and the cathode of the direct current constant flow source (1) is connected with a copper electrode; the lower end of the copper electrode is immersed in the electrolyte of the electrolytic bath (3); an input end of the electric current measurement device (2) is connected with the direct current constant flow source (1); and an output end of the electric current measurement device (2) is connected with a testing product, and meanwhile, testing data is transmitted to the control monitoring system (5) through a transmission line. The testing device for the direct current porcelain insulator cap corrosion mechanism research, provided by the invention, has a simple structure, and is convenient to use, and the testing method for the direct current porcelain insulator cap corrosion mechanism research, provided by the invention, is simple and convenient to operate, and is convenient and practical.