Abstract: In order to explore the significance of shelf sea in the global biogeochemical cycle of marine carbon monoxide (CO), the distribution, flux, dark production and microbial consumption of CO were investigated in the East China Sea during spring in 2021. Atmospheric CO mixing ratios ranged from 126.07 × 10⁻⁹ to 353.15 × 10⁻⁹, with an average of (191.32 ± 51.52) × 10⁻⁹, showing an obvious decreasing trend from coastal waters to open sea. The concentrations of CO in the surface seawater ranged from 0.83 to 4.08 nmol/L, with an average of (2.07 ± 0.84) nmol/L. The highest value appeared near Zhoushan Islands and the lowest value was measured at sampling stations at night, presenting evident influence by solar radiation intensity and terrestrial organic matter. The result of vertical distribution of CO in coastal waters presented that high concentration of CO occurred in the surface seawater and then decreased with increasing depth. The supersaturation factors of CO in the surface seawater varied from 4.98 to 24.96, with a mean of (13.94 ± 5.77). The sea-to-air fluxes of CO ranged from 2.62 to 9.38 μmol/(m²·d) with the mean of (6.70 ± 2.62) μmol/(m²·d). In the incubation experiments of dark production of CO, the concentration of CO increased linearly with the increase of time. Dark production rate varied from 0.024 to 0.50 nmol/(L·h), with the average of (0.20 ± 0.14) nmol/(L·h). There was a linear correlation between a₃₅₀ and dark production rate of CO. Microbial consumption rate constants of CO varied from 0.034/h to 0.24/h, with the mean of (0.11 ± 0.08) /h. This research preliminarily investigates the dark production of CO in the nearshore area of China, which provides basic data for the construction of the biogeochemical cycle system of CO in the continental shelf area of China, and helps to deepen our understanding of the role of continental shelf areas in the biogeochemical cycle of CO in the global ocean.