Abstract: In order to analyze the interaction between electric field, temperature field and chemical reaction of combustion, and to accurately simulate the distribution of charged particles in the gap under the condition of vegetation flame, this paper establishes a DC gap multi-physical-field coupling model in which the strong coupling of chemical reaction under the condition of vegetation flame is taken into account. The key parameters of the model are set according to the results of vegetation burning test. The effects of different polarity voltages and electrode heights on the distribution characteristics of charged particles and the effects of charged particles on the background electric field are analyzed by using the model simulation. The results show that, under the test conditions, when the coefficient of the pyrolysis reaction equation of pine is modified to C₁₀H₁₄O₆→4C+3CO+CO₂+2CH₄+2H₂+H₂O and the pyrolysis reaction rate is 2.4×10^–8 mol/(m³·s), the simulation results are the closest to the test results. With the decrease of electrode height, the concentration of charged particles with different polarity near the electrode increases from 10^–9 mol/m³ to 10^–8 mol/m³, which is similar to the leakage current. The effect of charged particles on the initial background electric field near the positive electrode is greater than that of the negative electrode. The increasement of the background electric field near the positive electrode is 70%~110%, and the increasement of the background electric field near the negative electrode is 40%~80%.