In urban areas with many buildings, the transmission of 5G signals can be greatly absorbed or reflected, leading to decreased effectiveness of transmission. To address the issues mentioned above, the functional admixture formed by the mixture of nanocrystalline cellulose (NCC) and diammonium hydrogen phosphate (DAP) is added into concrete in this study, the electromagnetic transmission performance (ETP) and mechanical properties of concrete are enhanced simultaneously for the first time, and the electromagnetic transmission coefficient of concrete is doubled. When NCC and DAP are mixed, the electromagnetic transmission coefficient of concrete improved by 117.65%-124.35%, among which, when 0.5wt% DAP and 4wt% NCC are mixed, the electromagnetic transmission coefficient of concrete is the highest, and some frequency bands are as high as 70%, meeting the requirements of electromagnetic wave transmitting materials. In addition, the compressive strength of concrete containing 4wt% NCC and 0.5wt% DAP increases by 24.3% compared to concrete containing only 4wt% NCC.