Laboratory analysis was conducted to investigate soluble organic C content of paddy soils in subtropical China in relation to extraction conditions. Results showed that the concentration of water-soluble organic carbon (WSOC) increased with soil moisture, which was more obvious in soil higher than 600 g/kg in moisture content. WSOC was positively and significantly related to water-soil ratio, especially when the water-ratio was over 2. WSOC was not influenced by duration of the extraction when it was not longer than 5 h. Type and concentration of the extraction reagents influenced significantly the soluble organic carbon contents in soils, indicating a higher concentration of extraction reagent would bring out a higher WSOC. Based on the above findings, it can be concluded that to keep experiment results comparable, it is advisable to adopt a uniform extraction method, that is, ①fresh soil samples, 200~400 g/kg in soil moisture content; ②deionized water as extraction reagent; ③water-ratio being 2; ④ shaking and extraction for 30 min; ⑤centrifugation for 20 min (4000 r/min); ⑥0.45 μm membrane for filtration; and ⑦TOC analyzer to determine organic carbon in filtrate.