The utility model discloses a novel dynamic compaction machine which utilizes a touchdown bob-weight mechanism (8) and a bob-weight hoisting mechanism (9), wherein the bob-weight hoisting mechanism (9) can control the touchdown bob-weight mechanism (8) to contact to earth or leave earth, an inner work arm (11) is connected with an outer work arm (4) through an arm frame self jacking oil cylinder (10), so that elongation and shortening of the work arm are achieved; in addition, an arm head (12) at the upper end of the inner work arm (11) adopts a special fish belly structural style. The novel dynamic compaction machine is simple in structure and convenient to operate, fatigue properties of an arm frame are increased, different tamper level variation is facilitated by the lifting and descending of the arm frame, and complete machine runs well, and stability is high.