The invention relates to the technical field of engineering machinery, specifically to a rammer mechanism, a screed plate device and a spreading machine. The ramming mechanism comprises a front rammerbody, a rear rammer body, a front plunger chip and a rear plunger chip; the front rammer body is connected with the rear rammer body; the front plunger chip is arranged on the front rammer body; therear plunger chip is arranged on the rear rammer body; the front plunger chip and the rear plunger chip are arranged in parallel; a working part of the front plunger chip comprises a first plane and afirst groove formed in the first plane; a working part of the rear plunger chip comprises a second plane and a second groove, wherein the second plane is coplanar with the first plane, and the secondgroove is formed in the second plane; the first plane and the second plane can be used for ramming materials; and the first groove and the second groove can be used for accommodating big particles inthe materials and are distributed in the length direction of the front plunger chip in a staggered manner. As the first groove and the second groove are correspondingly formed in the front plunger chip and the rear plunger chip of the rammer mechanism, impact effects of the big particles on the working parts of the front plunger chip and the rear plunger chip are reduced, and the service life isprolonged.