The paper proposes a rational tangent halftoning algorithm with a single threshold matrix, which has different threshold matrices with different sizes of row and column for different screen angles respectively, in order to assume that all corners of the corresponding matrix are located on junctions of grid of laser imagesetter and that the shape and size of the halftone dot do not vary from halftone cell to halftone cell. So the complication of the proposed method can be less by avoiding interpolating, and the performance of the halftone by the proposed method is good, too. To assess the performance, this paper describes the formation of the threshold matrices and the procedure of halftoning of the proposed algorithm for 4 screen angles with halftone cell 16 times 16, and finally gives the corresponding halftones.