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Introduction: Intercropping has a potential to reduce the CO2 emission from farmlands. Limited information is available on the underlying reasons. Methods: This study investigated the effect of milk vetch (Astragalus sinicus L.) (MV), rapeseed (Brassica napus L.) monoculture (RS) and intercropping (Intercrop) on soil CO2 emissions, moisture and temperature in a bucket experiment during 210 days from October 2015 to May 2016 on Chongqing, China. Results: The results showed that soil CO2 efflux of MV, RS and Intercrop was 1.44, 1.55 and 2.08 mmol·m-2·s-1 during seedling and stem elongation stages and 3.08, 1.59 and 1.95 mmol·m-2·s-1 during flowering and podding stages. At seeding and stem elongation stages Intercrop had 1.4 times higher soil CO2 efflux than the mean of MV and RS. In contrast, MVhad 1.6 times higher soil CO2 efflux than Intercrop thereafter, which shows it was inhibited if milk vetch presents as Intercrop only. Decreased sensitivity of soil respiration to temperature in 1.4 times and lower soil moisture by Intercrop were found compared to MV. Intercrop decreased soil moisture, especially at the seedling and stem elongation stages, compared to the monoculture. The fluctuation on soil respiration in RS and Intercrop was slight with changes in soil moisture. Conclusion: Thus, milk vetch-rapeseed system has a potential to decrease CO2 emission from farmland, however soil moisture should be regulated properly. [ABSTRACT FROM AUTHOR]