The utility model belongs to the field of knife rest performance detection technique and discloses a numerical control knife rest's performance parameter on -line measuring device solves present blade block performance parameter and need artificially switch sensor, the low problem of detection efficiency in detecting, including servo tool rest, mounting platform and knife rest performance parameter on -line measuring device, knife rest performance parameter on -line measuring device comprises knife rest detection device main part and vibration sensor automatic exchange device, knife rest detection device main part includes that blade disc positioning accuracy and tool changing speed detection device, blade disc vibration detection device, cutter arbor vibration detection device, knife rest operation noise detection device and cutter arbor are out of shape detection device, examine measure and regulate mould preparation piece and the synchronous rotary die piece that revolves to neutrality, vibration sensor automatic exchange device includes electromagnetism clamping jaw, servo motor and worm gear revolving platform, the utility model discloses with the sensor design that detects to one set of complete on -line measuring device, adjust according to different knife rests, simple to operate is nimble, the suitability is strong.