The influences of CO2 on the characteristics of a limiting current oxygen sensor in CO2- O2-N2 atmospheres were investigated. The studies indicated that the I-V curves appeared two-stage current plateau at (0~2) V operation voltage in CO2-O2-N2 atmospheres with CO2 concentration changed from 2.03% up to 12.18% and oxygen concentration remained at 5%、7.5%、10%, respectively. The first saturated current IL1 appeared in the voltage range of 0.8～1.4 V while the second saturated current IL2 appeared in 1.65～1.82 V, respectively. The difference between the two current platforms (IL2-IL1) and (-ln(1-XCO2)) showed a good linear relationship. And the oxygen sensor’s up-response time and down-response time to CO2 were both within 30s. The concentration of CO2 can be detected at a high working voltage.