The invention discloses a straw pulverizing and scattering machine with a uniform feeding device, and belongs to the field of agricultural equipment. The straw pulverizing and scattering machine comprises the uniform feeding device, a pulverizing roller device, a flow guiding and scattering device, a transmission device, a fixed cutter device and a machine shell. The uniform feeding device is arranged below a straw outlet in the tail of a combined harvester, and the pulverizing roller device is arranged on the lower edge of the tail of the combined harvester. A uniform feeding roller in the uniform feeding device can accelerate straw, borne by a straw receiving plate, at a straw outlet, and the problem of straw blockage is solved. The accelerated straw is evenly fed into the whole pulverizing work width of the pulverizing scattering machine under the flow guiding action of flow guiding plates different in angle. Due to the special shape design of a flail knife, the pulverizing roller device can generate strong wind power during high-speed rotation cutting of the straw, the straw discharging speed is increased, and the straw scattering width and the scattering uniformity are improved; the angle of the fixed cutter device is adjustable, accordingly, the most beneficial cutting angle of the straw is reached, the pulverizing effect is improved, and power consumption is reduced.