Abstract: The greenhouse vegetable production has become one of the most promising agricultural industry in China with a rapid increase of planting area during the last two decades. Over-fertilization combined with improper irrigation dramatically increases nutrient losses and environmental pollution. However, the absence of surface soil, high temperature and moisture usually lead to low content on soil organic carbon and rapid soil mineralization in the sunken greenhouse vegetable production, northern China. Accumulation of soil organic carbon is slow even when straw is applied for a long period with conventional flooding irrigation. Promoting the sustainability of intensive used solar greenhouse vegetable production by optimizing irrigation and straw application management may have a positive impact. Our study in this paper focused on 1) whether straw returning can decrease mineralization rate of soil organic carbon and increase its accumulation with drip irrigation; and 2) suitable sampling schedule to measure daily CO2 emission flux. A two-factor field experiment with three replicates was carried out which included two irrigation methods, i.e. conventional flooding irrigation fertilization and drip irrigation. Fertilization was combined with straw application rate of 0 and 3 500 kg/hm2. The four treatments are: conventional flooding irrigation with over-fertilization according to farmer’s practice (CIF); CIF + maize straw (CIF+S), drip irrigation with optimizing fertilization (DIF); and DIF + maize straw (DIF+S). Each plot (6.7 m × 3.6 m) consisted of three raised beds (0.7 m in width) and the walk way was 0.5 m in width between the raised beds. One of the three raised beds was used for measuring the fruits yield, one for monitoring CO2 emission and other one for collecting soil and plant samples. In order to minimize lateral seepage of water and nutrients, we separated the plots with impermeable film to the depth of 0.6 m. One-month-old tomato seedlings were transplanted on raised beds with a handheld transplanting tool. Four fruit clusters were retained at each growing season and each cluster reserved four fruits. Gas flux chambers were composed of a permanent frame (50 cm width × 50 cm length × 20 cm depth) that was pre-installed in each plot before transplanting, and the height of top sampling chambers was 50 cm. The CO2 fluxes were on line determined daily by using of CO2 infrared spectrometer over the growth period between 08:00 am and 09:00 am at 30-second intervals during the closure time of 4 min (i.e., at time 0 and after 30, 60, 90, 120, 150, 180, and 240 s). The CO2 gas fluxes were calculated from the slope of linear regressions of gas concentrations against the chamber closure time. The results showed that no significant difference on soil CO2 emission flux was found between the measurements from 08:00-09:00 am and the daily average, and they were significant positively correlated, the coefficient of determination between was 0.987, while CO2 emission measured in other time intervals were significantly different from daily average. Moreover, compared with conventional irrigation fertilization, the accumulated CO2 emissions was significantly decreased in drip irrigation fertilization without reduction of the tomato fruit yield, regardless of whether straw was applied or not. In addition, the peak of CO2 emission occurred during 8-15 d after transplanting, then CO2 emission decreased and then stabilized. The difference of daily CO2 emission flux among treatments can only be detected within 40 days after transplanting, and afterward there was no significant difference among treatments. Finally, there was a significant positive correlation between cumulative CO2 emission and soil temperature. Our results demonstrated that drip irrigation fertilization can significantly reduce soil CO2 emission and potentially improve the soil organic matter accumulation in the sunken solar greenhouse vegetable production.