The invention discloses a testing method of a continuous scratching interference behavior of a single abrasive grain of a black metal test piece pre-repaired by a CBN tool and belongs to the fields of material performance testing and precise and ultra-precise machining during machining. Due to the fact that the black metal test piece is fixed to an electric main shaft and subjected to online dynamic balance; then the CBN tool is adopted for repairing a disk of the test piece, and the requirements for end face bouncing and roughness required for testing are met; a tool bit with the top end fixedly connected with the single abrasive grain is installed through replacement, and tool setting is performed in the replacement process; finally, a scratching test is started, the test piece rotates at an assigned speed, the tool bit performs radial feeding at assigned cutting depth, interference spiral scratches are formed on the end face of the test piece, and a measurement system acquires scratching force, an acoustic emission signal and other physical quantity in the process. The method can simulate the interference behavior between abrasive grains in the high-speed grinding process. A relevant testing result can be used for deep research of a grinding mechanism and optimization of grinding parameters.