This paper reports the extraordinary properties and industry applications of Nd: YAG Microchip Laser Feedback Interferometer, Nd: YAG LFI. The Michelson interferometer has been invented for more than a century and is widely used in science and industry today. The Nd: YAG LFI, which is based on laser feedback effect instead of ordinary interferometry, has the different structure from Michelson interferometer, and then extraordinary properties. Therefore the Nd: YAG LFI can be used as a traditional laser interferometer with nano-meter resolution and a few meters measurement range. At the same time Nd: YAG LFI can also measure the displacement of light, thin, black, transparent (water, alcohol, glass surface) objects, even liquid evaporation rate. Some actual applications are described in this paper, including the displacement measurement with nano-meter resolution for black machine parts, measurement of evaporation rate of liquids, measurement of the hysteretic curves of PZT and displacement measurement of cylinder surface. Based on Nd: YAG LFI, the Laser confocal feedback profilometry (LCFP) has been studied. The nanometer resolution has been achieved for the glass surface and optical gratings measurement.