A flywheel torsion measuring device with internal power, applied to a shaft and a flywheel of sports equipment, has a wheel connector, a power unit, a torsion measuring element and circuit boards. The wheel connector, for fastening the flywheel and connecting the shaft through a bearing, has an assembly space and an annular plate. The power unit provides a power. The torsion measuring elements are disposed on the annular plate of the wheel connector, and the circuit board, which is disposed in the assembly space of the wheel connector and electrically connects the power unit and the torsion measuring elements, converts the power into a working power for the torsion measuring element. The wireless transmission module of the circuit board transmits the measurement information generated by the torsion measurement component to the outside.