To study the disturbance effect of forest fire on the carbon cycle of coastal sandy forest ecosystem, taking Eucalyptus urophylla × Eucalyptus grandis plantation and Casuarina equisetifolia plantation as research objects, the LI-8100 soil CO₂ flux automatic measurement system was used to measure the soil CO₂ flux of burned and control plots in different plantations. At the same time, soil temperature and moisture, soil pH, total carbon, total nitrogen and mineral nitrogen contents in the sample plots were measured. The relationship between soil CO₂ flux and water and heat factors as well as the changes of soil physical and chemical properties were analyzed. The results showed that the soil CO₂ fluxes in the burnt plots were significantly lower than those in control plots, the monthly average of soil CO₂ fluxes in the E. urophylla × E. grandis forest burned plots and the control plots was 2.47 and 3.32 μmol/(m²·s), respectively, and that in C. equisetifolia forest was 2.48 and 3.28 μmol/(m²·s), respectively. After the forest fire disturbance, the soil temperature and moisture of the two shelterbelt forests were higher than those of the control plots, in the exponential function model, soil temperature at 10 cm of E. urophylla × E. grandis and C. equisetifolia forest explained 10.4%~21.4% of the total soil respiration. In the binomial function model, soil moisture at 10 cm in E. urophylla × E. grandis forest and C. equisetifolia forest explained 15.8%~29.4% of the total soil respiration. In the bivariate regression model, soil temperature and humidity and their interaction together explained 33.1%~66.8% of the total soil respiration. Mild fire disturbance had little effect on soil pH, total carbon, total nitrogen and mineral nitrogen content in E. urophylla × E. grandis and C. equisetifolia forest, the soil pH of the burned area in the two types of forest both increased, and the contents of NH₄⁺-N and NO₃^--N decreased. In summary, forest fire disturbance would significantly reduce soil carbon emission of two shelterbelt forests in the study area. The fitting effects of the bivariate model of soil temperature and humidity in different plots were all better than those of the single factor-model, indicating that soil carbon emission was affected by both, which could provide reference data and theoretical support for the research on the impact of forest fire disturbance on the soil carbon balance of coastal sandy shelter forests under the background of climate warming.