A field experiment was conducted to study the contents of organic carbon, total nitrogen, dissolved organic carbon, dissolved total nitrogen and readily oxidized organic carbon in spring maize field under three different environmental conditions:Natural atmospheric CO₂ concentration (as the control, marked as CK), open-top chamber (OTC) system with CO₂ concentration of 700 μmol/mol (marked as OTC+CO₂) and OTC system with current atmospheric CO₂ concentration (marked as OTC). The results showed that compared with OTC, the elevated CO₂ had no significant effect on the contents of soil organic carbon, total nitrogen, dissolved organic carbon and readily oxidized organic carbon (P > 0.05), but decreased the dissolved total nitrogen by 18.17% (P<0.05) at V12 stage, and increased the dissolved total nitrogen by 108.56% (P<0.05) at R3 stage. Compared with CK, OTC+CO₂ treatment decreased the soil organic carbon (expect R6) and total nitrogen (expect V12) during the whole period of maize, by 4.47%~14.42% and 6.78%~12.48% (P<0.05), respectively. The OTC+CO₂ decreased the dissolved organic carbon at V6 stage, dissolved total nitrogen at V12 stage and readily oxidized organic carbon at R1 and R6 stages; but increased dissolved organic carbon at R3 stage (P<0.05). In conclusion, the elevated CO₂ had no significant effect on organic carbon and its fractions, total nitrogen, but significantly affected dissolved total nitrogen. The impact of OTC on the results could not be ignored when using the OTC system to do the research about elevated CO₂ concentrations.