Nanometrology is the measurement standard of nano-materials and nanom eter devices,which is important for the development of nano-scicence and nano-technology.A nanometrology system based on laser multiple-feedback effect is presented is this paper. This nanometrology system consists of two parts:a plane mirror and a concave mirror,which is also called parallel-concave feedback cavity.The high density cosine-like intensity fringes with phase-qua drature are obtained due to the laser multiple reflections in the parallel-concave feedback cavity.The intensity of fringes is dozens of times of that of conventional weak feedback.The feedback fringes have nanometer level resolution without any electronic subdivis ion and can be traceable to the light wavelength.Two polarization polarized feedback fringes are obtained by using a birefringence du al-frequency laser.Especially,there is a phase difference between the two polarization polarized fringes.The phase difference is mainly determined by the frequency difference of laser,the length of external cavity and the feedback order.Furthermore,the di rection of displacement can be determined conveniently by using the phase relationship between two polarization polarized fringes.The experimental results compared with laser interferometer demonstrate that the linearity is better than 5.2×10－5,optical resolutio n is 10.2nm,and the measuring range is more than 500μm.