In order to achieve in-situ measurement of Double-Crystal Monochromator(DCM) stability, an angular vibration measuring system based on dual-frequency interferometers is designed, and a measurement platform is also established. A laser is split into two beams with an interferometer and then is aimed at the crystal surface. Reflective signals from both ends of the crystal are demodulated by a data acquisition board and the crystals′ angular displacement information is acquired at high frequency. Its frequency information can also be obtained by means of Fast Fourier Transform(FFT), from which the primary source of vibration that influences the stability of the monochromator can be deduced. We can achieve high-frequency acquisition of crystal angular displacement with a resolution of up to 25nrad.With this, information on the different sources of vibration can be distinguished, which can be significant in DCM structure optimization.