Abstract: On the basis of considering the influence of resin flow on the curing temperature field, the resin flow was introduced into the classical thermo chemical model. In addition, in consideration of the time-varying characteristics of material properties during curing process, the heat-fluid-solid multi-field strongly coupled finite element model was established. It can be found through the comparison with the references in which the effect of resin flow on the temperature field is not considered, the maximum temperature difference is lower, the thickness accuracy is higher, and the model reliability is better. Based on the established heat-fluid-solid strongly coupled finite element model, the curing process of composite structure with variable thickness section was numerically simulated. It is found that the obvious distribution gradient of temperature field, curing degree field and resin flow field exists in the thicker composite structure, and the distribution of fiber volume fraction is uneven. This is related to the structure thickness, the temperature transfer lag of different zones and the influence of the local resin flow on the effects of curing. With the thickness of variable cross-section composite structures increasing from 3.52 mm to 42.24 mm, the maximum temperature increases from 0.3℃ to 34.3℃, and the nonuniformity of the fiber distribution increases from 0.1% to 1.3%.