To expand the utilization of iron tailings, four kinds of porous ceramics were prepared by foam gel-casting with pressureless sintering, foam gel-casting with reactive sintering, and mold forming with reactive sintering using fine-grained high-silicon iron tailings, iron tailings + graphite, and iron tailings + graphite + silicon carbide as raw materials, respectively. DSC-TG and XRD analysis was applied to investigate the sintering process of iron tailings and the carbothermal-reduction reaction between iron tailings and graphite. The four porous ceramics’ porosities, compressive strengths, and thermal conductivities were further analyzed. The results show that the porous ceramics made only from iron tailings possesses high porosity (87.2%), compressive strength (1.37 MPa), and low thermal conductivity (0.036 W/(m·K)), meeting the requirement of thermal insulation material. Silicon carbide porous ceramics with improved thermal conductivity but a slight sacrifice of strength can be fabricated through carbothermal reduction between iron tailings and graphite. Moreover, the compressive strength of silicon carbide porous ceramics can be significantly increased by adding some silicon carbide to the raw materials. The silicon carbide porous ceramics achieved high porosity of 91.6%, high compressive strength of 1.19 MPa and thermal conductivity of 0.31 W/(m·K), which can be a guarantee of a carrier for composite phase change materials or light thermal conductive materials. Compared with foam gel-casting, the mold-forming process can significantly improve the thermal conductivity (1.15 W/(m·K)) of silicon carbide porous ceramics and greatly reduce the cost of raw materials and manufacturing, which is profitable for industrialization.