A novel reflection scanning near field optical microscope(RSNOM) which uses a fiber probe as both the light source and detector was developed. By means of interference detecting and polarization beam splitting detecting, the RSNOM eliminated the background noise disturbance which is commonly encountered in this kind of SNOM, and a high optical signal/noise ratio was achieved. Moreover, by vertically vibrating the sample, the light signal was modulated and detected with a lock-in amplifier, and the light intensity gradient imaging of the sample surface was realized, which further improved the image quality.This research shows that the RSNOM could detect the evanescent near-field wave effectively, and the image with a super-diffraction-limit resolution was obtained.