The invention provides an adjustable attenuator which comprises a main body, a transmission line, an absorber, a signal input head, a signal output head, a water cooling radiator, a display panel andan adjusting mechanism, wherein the transmission line and the absorber are arranged in the main body, the signal input head and the signal output head are electrically connected with the transmissionline, and the signal input head and the signal output head are respectively arranged on the two sides of the main body; the absorber and the transmission line are mutually coupled and are arranged inthe main body in a sliding mode; the water cooling radiator is arranged outside the main body, the water cooling radiator comprises a cooling water pipe arranged on the peripheral side of the main body in a winding mode, on end of the cooling water pipe is connected with a water tank, and the other end of the cooling water pipe is connected with the water tank through a variable speed water pump;the display panel is arranged on the outer surface of the main body; the adjusting mechanism is arranged on the main body, and the adjusting mechanism is connected with the absorber, an adjusting partof the variable speed water pump and the display panel and is used for synchronously adjusting the radial motion of the absorber along the transmission line, adjusting the rotation speed of the variable speed water pump and adjusting displayed numerical values of the display panel. The adjustable attenuator can adjust attenuation and can be suitable for different line situations.