The invention relates to an inner-hole measuring unit, which is a critical component at the testing equipment for measuring bearing inner hole in full automation or the inner of hardware cutting piece. The inner-hole measuring unit is an integrator which is formed by connecting a driver with a measuring mechanism. The measuring mechanism is composed of dynamic and static measuring benches, dynamic and static measuring heads with measuring point, a sensor, a measuring cylinder, an adjusting screw, a measuring plane, a pressing board, a crossing reed, a spring and a standard working piece; the measuring positions of the dynamic and static measuring benches are three measuring points; a change ring surface contact is a three point contact and self centering; the measuring mechanism is arranged on the dynamic and static measuring benches; the inner-hole measuring unit has the advantages of simple and compact structure, compact size, easy assembly and maintenance. The dynamic and static measuring heads are connected as a whole by the crossing reed, so that a lever measuring pivot is constant; simultaneously, the sensor which is arranged at the measuring bench can be changed along the tiny change of the measuring bench; the measuring accuracy is high and the measuring effect can not be affected. An original position automatic standard piece, a measuring protection limit and a force-measuring governing device are also arranged to ensure the safety and accuracy of the measurement.