The invention discloses a flattening device for chain type paper of a printer. The flattening device is mounted on a fixed bracket, and comprises at least one flattening assembly; the flattening assembly is provided with at least one paper flattening mechanism; the paper flattening mechanism comprises a driving roller and a driven roller which can rotate; the driving roller is supported on the fixed bracket in a rotatable manner; the driven roller is supported on the fixed bracket in a rotatable manner; a flattening channel for flattening paper is formed between the driven roller and the driving roller; and one side surface of paper in the flattening channel is in close contact with the driving roller, and the other side surface of the paper is in close contact with the driven roller. Theflattening device disclosed by the invention can change messy stress on multilink (including single-link) printer paper with various widths and lengths, so that the stress is uniformly distributed, and forward stress is increased; paper burrs are removed, so that the paper is flatter; and the aim of reducing the paper blocking rate during link separation and printing is fulfilled.