Abstract: Aiming at the problems of low offline measurement efficiency, large secondary clamping error and poor deep hole measurement accessibility in the hole machining of slender tubular parts, an on-machine measurement method based on dual-spectral confocal sensors is proposed. Firstly,this method adopts a symmetrical layout of dual sensors to synchronously collect data of measured points on both sides of the hole wall. Secondly,it obtains multi-cross-section diameters along the full hole depth through rapid axial generatrix scanning, and realizes roundness error measurement in combination with the indexing rotation of the workpiece. Finally, the measurement accuracy of the system was verified using a standard ring gauge set. Experimental results show that the measurement accuracies of bore diameter and roundness by this method reach 0.008 9 mm and 0.005 7 mm respectively. It satisfies the measurement requirement that the bore diameter and roundness measurement accuracy of slender parts is better than 0.01 mm, and achieves high-efficiency and high-precision on-machine measurement of slender parts.