The invention belongs to an optical assembly of optical detection equipment, and particularly relates to a double-arm sweep pendulum type interferometer system comprising a beam splitting mirror which is arranged on a pedestal, and a reflection channel which is composed of a first reflecting mirror and a second reflecting mirror. One end of the reflection channel is provided with a first backward reflecting mirror which is perpendicular to the transmitted light beams and a second backward reflecting mirror which is perpendicular to the reflected light beams. The first and second reflecting mirrors are arranged in a swing way relative to the pedestal. The mirror surfaces of the first and second reflecting mirrors are maintained to be parallel constantly in the swing process, and the rotating axes are perpendicular to the plane in which the transmitted light beams and the reflected light beams are positioned. The characteristics of the double-arm sweep pendulum type interferometer system are that returning of the light beams through the original path is realized by utilizing the plane mirrors without sensitivity to inclination firstly so that calibration of equipment is facilitated; and then linear movement of the moving mirrors is changed into sweep pendulum movement of the platform so that moving mirror driving complexity can be reduced by sweep pendulum movement in comparison with linear movement, and realization is easy.