The invention provides a cutting knife for collecting natural rubber and a cutting method of the cutting knife. The cutting knife for collecting natural rubber are arranged on a rubber tree, wherein aY-shaped slot is formed in the rubber tree, the cutting knife includes a fixing component, a No. 1 arc chute, a telescopic rod, a second arc chute, an adjustment mechanism, a cutting assembly, a connecting plate, a connecting base and an insertion rod. According to the cutting knife for collecting natural rubber and the cutting method, through mutual cooperation of the Y-shaped slot, the fixing component, the No. 1 arc chute, the telescopic rod, the No. 2 arc chute, the adjustment mechanism, the cutting assembly, the connecting plate, the connecting base and the insertion rod, a Y-shaped wound can be formed in the surface of the rubber tree, and when the Y-shaped wound is compared with traditional arc wounds, the distance between overflowing gum at the highest point of the wound and a collection vessel at the lowest point is much shorter through the Y-shaped wound, so that the collection efficiency is improved, solidification, caused by long-time contact with the outside, of the gum is prevented, and negative effects on the flow of the gum at other positions are avoided.