Poor flowability of printable powders and long preparation cycles are the main challenges in the selective laser sintering (SLS) of chopped carbon fiber (C_f) reinforced silicon carbide (SiC) composites with complex structures. In this study, we develop an efficient and novel processing route in the fabrication of lightweight SiC composites via the SLS of phenolic resin (PR) and C_f powders with the addition of α-SiC particles combined with the one-step reactive melt infiltration (RMI). The effects of α-SiC addition on the microstructural evolution of the C_f/SiC/PR printed bodies, C_f/SiC/C green bodies, and derived SiC composites were investigated. The results indicate that the added α-SiC particles play an important role in enhancing the flowability of raw powders, reducing the porosity, increasing the reliability of the C_f/SiC/C green bodies, and contributing to improving the microstructure homogeneity and mechanical properties of the SiC composites. The maximum density, flexural strength, and fracture toughness (K_IC) of the SiC composites are 2.749±0.006 g·cm⁻³, 266±5 MPa, and 3.30±0.06 MPa·m^1/2, respectively. The coefficient of thermal expansion (CTE, α) of the SiC composites is approximately 4.29×10⁻⁶ K⁻¹ from room temperature (RT) to 900 ℃, and the thermal conductivity (κ) is in the range of 80.15–92.48 W·m⁻¹·K⁻¹ at RT. The high-temperature strength of the SiC composites increase to 287±18 MPa up to 1200 ℃. This study provides a novel as well as feasible tactic for the preparation of high-quality printable powders as well as lightweight, high-strength, and high–κ SiC composites with complex structures by the SLS and RMI.