Presents small confocal inspection technology which is developed by incorporating a gradient index lens for non contact high precision measurement of small internal contours, and which combines high axial resolution and absolute position traceability of a confocal microscope with a small gradient index lens. This technology features a high axial resolution, small in volume, aim at lope surface, and absolute step position traceability. the Piezoceramic is used as an axial driving device ,with a linear range of ±5 μm and 2 nm displacement per driving step drived by triangular waveform voltage signal, and the displacement sensor with a linear range of ±50 μm and a axial resolution of 1 nm used as a position tracer. Experimental result shows the non continuous contours tracking and aiming can be achieved with a resolution of 10 nm and in a range of ±1 μm for a angle gauge block of less than 20 degree.