A printing mechanism for a sample container is provided with a receiving end provided with a receiving rack, the receiving rack being connected with a fixed receiving plate and a movable receiving plate, wherein corresponding receiving trough and falling channel are formed by splicing and separating the fixed receiving plate and the movable receiving plate; and a discharging end provided with a rotating assembly that receives a sample container falling in the falling channel and drives the sample container to rotate to align an unprinted blank region on the sample container with a printing assembly.