The invention discloses a steel component deformation detecting instrument and a use method thereof. Two sides parallel to a measuring rod are provided with sensor slideways. One end of the measuring rod is provided with a slideway sensor for receiving signal. A displacement meter is arranged at the upper surface of a displacement meter pad which is arranged at the upper surfaces of the sensor slideways. A fixed vertical rod is vertically arranged at the upper surface of the displacement meter pad. The top of the fixed vertical rod is provided with a Bluetooth camera. According to the steel component deformation detecting instrument and the use method thereof, sensor devices are employed by electromagnets and slideways, through a computer digital control switch, the operation is simple, the measurement metering of the displacement meter can be realized by controlling shooting through computer software by the Bluetooth camera fixed on a pad fixed rod, and for a long steel component, a measurement requirement can be satisfied through connecting the measuring rod.