Ultrafine TaC-5%Co composite powders were synthesized by spray conversion process using tantalum oxalate solution and cobalt nitrate hexahydrate(Co( . 6). The phase of Ta-Co oxide powders had amorphous structures after calcination below 50 and changed , and phase by heating above . The calcined Ta-Co oxide powders were spherical agglomerates consisted of ultrafine primary particles <50 nm in size. By carbothermal reaction, the TaC phase began to form from 90. The complete formation of TaC could be achieved at 105 for 6 hours. The observed size of TaC-Co composite powders by TEM was smaller than 200 nm.