Abstract: LTE-M system is intended to be used in the next generation of rail transit system, in which more than one leaky coaxial cables(LCX) are employed to establish the multiple-input multiple-output(MIMO) system. Therefore, the system performance depended on the configuration should be studied. Based on the time domain channel measurement methodology and MIMO channel theory, we carried out channel measurements to investigate the MIMO performance using double LCXs in a typical tunnel scenario at the frequency of 1.8 GHz. We used different polarizations of LCX and different LCX spacings to analyze the MIMO channel correlation. We find that when the polarization of receiving antenna is vertical and polarization of two LCX are horizontal, the best MIMO performance will be shown. Thus, the MIMO performance is not strictly dependent on the LCX spacing.The results provide a reference for the deployment of LTE-M in the future.