To obtain the weak signal light detection from the high background noise, a study on ultra-narrow bandwidth Faraday anomalous dispersion optical filter (FADOF) at the 87Rb D1 line, 5S1/2F=2→5P1/2 F′=1transmission (795 nm) is demonstrated experimentally. A sample cell filled with Rubidium atoms in which the proportion of 87Rb is greater than that of the nature rubidium is placed in a homogeneous magnetic field between two crossed Glan-Thompson polarizers. The incident probe light goes through the sample cell, and interacts with the atoms.Because of the Faraday rotation, the function of the filter can be realized. When the experiment condition changed, the result of transmission spectrum changed accordingly. With the temperature rising from 340 K to 360 K, the variation of the transmission spectrum is recorded particularly.And the reason for the variation is analyzed carefully. At a proper temperature and magnetic field, a transmission spectrum narrowed to ~220 MHz is obtained, and the peak transmission is about 48%. The performance of the87Rb D1 line is better than that of the 85Rb.