The invention discloses an axial flow type mud pulse slow release machine. The axial flow type mud pulse slow release machine comprises a cavity filled with inert gas; the cavity includes a cover and a rubber inner cylinder; two ends of the rubber inner cylinder are respectively connected with a first outlet pipe and a second outlet pipe; and the inner diameters of the first outlet pipe and the second outlet pipe are the same, and are smaller than the inner diameter of the rubber inner cylinder. The axial flow type mud pulse slow release machine reduces pressure fluctuation and flow pulsation in an absorption pipeline through the large-diameter cavity and the inert gas filled between the rubber inner cylinder and an outer cylinder. In addition, an adjustable mechanism is designed by using a mud inlet pipe with a rectangular thread, an added pre-pressure spring and self elasticity of the rubber inner cylinder; and an adjustable rotating drum out of an end cover rotates to stretch the rubber inner cylinder to change the rigidity of the rubber cylinder to adapt to mud currents with different parameters so as to achieve an effect of reducing the mud pulse to the maximum extent. Finally, the mud pulse slow release machine adopts a split design; and although the part number is relatively increased, the part manufacturing difficulty is reduced.