The C/C–Ti₃SiC₂ composites were prepared by reactive melt infiltration (RMI) using TiC powder, Ti powder, Si powder, and Al powder as raw materials. The effects of different molar ratios of raw materials on the phase composition, microscopic morphology, flexural strength, thermophysical properties, and electromagnetic shielding effectiveness of the composites were investigated. The results show that the composites prepared with the ratio 1.8TiC/1.2Ti/1.4Si/0.2Al have a higher Ti₃SiC₂ content and exhibit better mechanical properties, thermal conductivity, and electromagnetic shielding performance: the flexural strength increases from 103.02 MPa ± 8 MPa to 150.50 MPa ± 7 MPa; the thermal conductivity ranges from 12.651 W/(m·K) to 15.193 W/(m·K) at temperatures from room temperature to 1000 ℃; and the electromagnetic shielding effectiveness increases from 21.40 dB to 26.68 dB in the 8.2–12.4 GHz frequency range. Analysis of the phase composition and microscopic morphology of three groups of samples reveals that as the TiC to Ti molar ratio decreases, the difficulty in forming Ti₃SiC₂ gradually increases, mainly because the Ti content plays a key role in both the formation of the liquid phase during the reaction and the extent of the reaction.