The invention discloses a three-dimensional printer and a control method and belongs to the technical field of mechanical tools. The three-dimensional printer comprises a feeding device, a mechanical arm device and a printing execution device. Both the feeding device and the mechanical arm device are fixed to a fixed base plate. The printing execution device is connected with an end executor of the mechanical arm device. The feeding device is connected with the printing execution device through a protective hose. A printing contour is described through a spline B, and then control over the movement of the printer is achieved. According to the three-dimensional printer and the control method, the movement of the three-dimensional printer is controlled through a mechanical arm and spline B interpolation algorithm, and rapid and accurate positioning in the three-dimensional space can be achieved; in addition, the structure of the three-dimensional printer is compact, and thus the three-dimensional printer can be placed in a narrow space; and the three-dimensional printer has high positional accuracy.