Abstract: A sharp-rejection low-pass filter (LPF) with excellent rectangle characteristic is proposed in this paper using a novel DGS. The precise transmission coefficient of the novel DGS is obtained through FDTD analysis. The results of FDTD simulation and measurement in the references verify the validity of the FDTD method. The influences of lattice dimensions on the characteristic of frequency are studied.The influences of straight microstrip line on the characteristic of frequency are also studied in this paper. A method about controlling the cut-off frequency by altering the length of straight microstrip line or the lattice dimensions is presented and discussed. The relationship given in the paper will provide a powerful tool for the analysis and design of LPF using the novel DGS.