The utility model relates to a rotatory monitoring devices of main shaft. Pass through the fix with screw on the terminal surface of main shaft and send out the news board, it is rotatory along with the main shaft, pass through the nut with a news board complex inductive pick -up and fix on the protection casing, the protection casing is fixed on the base, the inductive pick -up be connected with PLC. Its simple structure, easily assembly, the operation is reliable.