The utility model provides an adjustable optical attenuator comprising a double-pore capillary tube, a focusing lens, a micro-reflective mirror, and a microelectronic mechanical system, wherein, the end surface of the double-pore capillary tube, which is next to the focusing lens, and the plane vertical to the axial direction of the optical attenuator, form a first included angle Delta; the end surface of the focusing lens, which is next to the double-pore capillary tube, and the plane vertical to the optical attenuator, form a second included angle Gamma; and the absolute value of the difference of the first included angle Delta and the second included angle Gamma is more than three degrees. The adjustable optical attenuator provided by the utility model can compensate the insertion loss of incident light with shorter wavelength during the large attenuation, and effectively lowers the loss relevant to the wavelength.