Abstract: Targeting the specific scenario of 5G millimeter wave applied in metro tunnel in the future, the channel correlations of 28 GHz millimeter wave in tunnel environment is calculated by field test and ray tracing simulation, and the influences of the antenna array position and different polarization configuration on the MIMO channel characteristics are obtained. Results show that simulation results are highly matching with field measurement results, validating the results of ray tracing simulation. Experiment results show that HH (horizontal polarization) encourages better MIMO performance in 5G millimeter wave communications in the tunnels.