The invention provides a CFD-based transformer respiratory system capacity matching evaluation method. The method comprises the following steps: establishing a full-size three-dimensional model of a to-be-evaluated transformer and a respiratory system thereof; then, dividing a calculation domain, then setting boundary conditions and physical parameters of materials, then setting a theoretical model and a solving algorithm, setting initial conditions, calculating heat productivity and taking the heat productivity as a heat source, and finally, performing simulation to obtain oil conservator oillevel cloud chart data under different load coefficient conditions, thereby obtaining the adaptation condition of a respiratory system and a transformer. The adaptability of the transformer and the respiratory system is rapidly and accurately calculated through the CFD technology, it is guaranteed that the capacities of the transformer and the respiratory system are well matched, serious accidents such as transformer oil overflow after operation are avoided while the capacity utilization rate of the respiratory system is increased, and safe, stable and economical operation of the transformeris guaranteed.