The invention discloses a PDL adjustable module, comprising an input end optical fiber used for inputting an optical signal, an input polarization maintaining coupler used for dividing the input optical signal into two paths of polarized light, an adjustable polarization maintaining attenuator used for adjusting the optical power of one path of polarized light output by the input polarization maintaining coupler, an output polarization maintaining coupler used for merging the polarized light output by the adjustable polarization maintaining attenuator with the other path of polarized light output by the input polarization maintaining coupler, and an output end optical fiber used for outputting the merged optical signal. The PDL adjustable module disclosed by the invention divides the input light into the two paths of polarized light by the input polarization maintaining coupler, and then realizes the adjustable insertion loss attenuation of one path of polarized light through the adjustable polarization maintaining attenuator, since different control voltages are applied to the adjustable polarization maintaining attenuator, the optical power of the path of polarized light adjusted by the adjustable polarization maintaining attenuator changes accordingly, therefore, the PDL adjustable module disclosed by the invention can realize adjustable PDL control, facilitate the research of the PDL change on the influence of a polarization multiplexing system.