The positioning system based on surface plasmon resonance (SPR) can achieve nanometer resolution and repeatility. A special retroreflector is designed that incidence angle of its first reflection surface is equal to resonance angle of SPR. Then the surface is coated with gold film and a fibre probe is put behind the film to build up a SPR positioning system. The special retroreflector is component of SPR as well as the measurement mirror of interferometer to implement their integration. At the beginning of a measurement, a zero position is determined by SPR positioning system. If there is drift during measurement, reset interferometer data to diminish drift as soon as the special retroreflector reaches the zero position. The interferometer at nanometer positioning integration system is set up. Experiments show that uncertainty of interferometer is reduced from 70 nm to 10 nm. The measurement precision and stability of interferometer is increased.