On the base of first order dynamic model,combining with a laboratory soil incubation experiment,the dynamics of soil organic carbon(SOC) decompositions,three carbon pool sizes and average turnover time are analyzed,including swamp soil,meadow soil,othic yellow brown soil and brown rendzina.The results show that these four soil types total soil organic carbon are 8.48~24.53 g/kg in the surface soil and 4.02~16.77 g/kg in the subsoil.The size of active SOC pool from surface and subsoil respectively accounts to 0.99%~5.01% and 1.31%~1.91% of total soil organic carbon,and the average turnover time is 8.8~14.3 days.Slow SOC pool,15.88%~59.04% and 20.43%~48.36%,1.3~29.1 years.Passive SOC pool,39.97%~79.11%,50.31%~77.66%.All the three pool sizes of those four soil types are more in the surface soil than subsoil.Cumulative emission of CO2 during incubation for 91 days is 165.99~2 429.57 mg/kg in the surface soil and 108.04~743.02 mg/kg in the sub soil.Decomposition rate order of these four soil types is swamp soil,meadow soil,brown rendzina and othic yellow brown soil,which direct interrelated with active SOC carbon percentage content.Curve fitting of SOC cumulative release amount during incubation showed that cubic equation can describe change trend,and the correlation has reached high significant level(P<0.01).