The invention provides a cluster well group cathodic protection DC distribution device, a manufacturing method and a protection method thereof. The device comprises a plurality of double resistance value segmented rotary varistors. One end of each double resistance value segmented rotary varistor is connected with a cathode of a cathodic protection DC power supply, and the other end is respectively connected to a corresponding oil well casing or a water well casing. The double resistance value segmented rotary varistor is composed of two single segmented rotary varistors connected in parallel.A metal protective box is arranged outside the double resistance value segmented rotary varistor. By replacing a non-segmented conventional rotary varistor with the resistance segmented rotary varistor, the device of the invention has characteristics of small size, light weight, large DC distribution power, small energy consumption, large resistance adjustment range and stable operation. It ensures the balanced potential difference between the wells in the cathodic protection process of the cluster well group, and normal cathodic protection current is provided for the cluster well group casing. The casing will be protected from corrosion.