The study was performed to investigate the changes of components and volatiles in citrus sudachi juice heated at 40, 50, 60, 70, 80 and $90^{\circ}C$. Total acidity, $^{\circ}Brix$, pH, organic acids, free amino acids, vitamin C, naringin, hesperidine, neohesperidin and volatiles were analyzed in fresh and heated citrus sudachi juices. The major organic acids were citric, malic and oxalic acids and their total contents were 5.27-5.48%. Citric acid content exceeded 92%, malic and oxalic acids were 3.6 and 3.2% in total orgainc acids. The organic acids decreased as heating temperature increased, but the their decreasing contents were 0.3% of total oraganic acids. Sixteen kinds of free amino acids presented in citrus sudachi juice. Major free amino acids were alanine, threonine, proline, aspargine, aspartic acid, serine, tyrosine, and trytophane and minor free amino acids were arginine, valine, glycine, lisoluecine, leucine and histidine. Free amino acids contents decreased as heating temperature increased. Vitamin C contents also decreased from 21.3 mg% to 17.3 mg% as heating temperature increased. Naringin, hesperidine and neohesperidin also slightly decreased from 304 mg% to 297.0 mg% as heating temperature increased. In the fresh and heated juices, a total of 50 volatiles were separated, of which 31 were identified. Limonene dominated in volatiles, followed by ${\gamma}-terpinene,\;{\alpha}-phellandrene$, myrcene and ${\alpha}-pinene$. ${\alpha}-Thujene$ presented in the fresh jucie but did not present in the heated juice above $50^{\circ}C$. However, ${\alpha}-Terpinolene$, terpinene-1-ol, ${\beta}-terpineol$, $cis-{\beta}-terpineol$, ${\alpha}-muurolene$, bicyclo(3.2.0)hept-6-ene, and mentha-1.4.8-triene did not presented in the fresh jucie but newly formed in the juice heated at $90^{\circ}C$.