Abstract—The coupling loss of the non-graded LCX(leaky coaxial cable) increases with the length of the LCX. To effectively solve this problem, a kind of graded LCX is designed. In this paper, the theoretical basis of the design of the LCX is expounded firstly. The HFSS is used to design and analyze the non-graded LCX and the graded LCX secondly. The modeling process uses MATLAB to model with HFSS-API program automatically. The results show that the design of the graded LCX can meet the coupling loss doesn’t increase with the length of the cable, which has some reference values for the design of the LCX.