The invention discloses a replaceable anti-collision intelligent device for a numerical control outer circle turning tool. The device comprises an ultrasonic radial detector, a fastening bolt, a PCB,a wireless transmitting module, an ultrasonic axial detector, a shell, a wireless receiving module, a display screen, a controller, a thyristor and keys. According to the device, the distance betweena tool nose and an obstacle can be automatically detected, a tool speed is calculated, a tool collision trend is automatically judged, and safety guarantee is provided for tool collision avoidance ofnumerical control turning. An ultrasonic sensor has a detachable function like a blade, and is accurate in detection distance and high in real-time performance, the controller can conveniently set a detection distance and a detection speed, different machine tool characteristics and actual machining requirements are met, and the flexibility is good. In the machining process, the anti-collision device can effectively avoid personal injury and machine tool damage caused by the fact that a tool collides with a workpiece or the obstacle, and the application prospect is wide.