Electromagnetic protection measures can effectively prevent electromagnetic waves from harming equipment, facilities, information security and human health. To enhance the electromagnetic wave-absorbing capacity of standard concrete, silicon carbide (SiC) was selected as an absorbing agent to produce wave-absorbing concrete. The influences of SiC content on the electromagnetic reflection loss, electromagnetic parameters, and mechanical properties of concrete were systematically investigated. After 28 days of curing, the concrete sample modified with 10 wt% SiC displays the compressive strength and splitting tensile strength of 36.12 MPa and 3.10 MPa, respectively. And the optimum electromagnetic absorption performance reaches −16.25 dB at 3.37 GHz and the electrical conductivity is 1.55×10−4 S/m. The SiC modified concrete demonstrates the dielectric loss type absorption characteristics. This research provides a practical solution for electromagnetic wave protection, which is expected to be used in both military and civilian applications.