The invention discloses a large-scale wind power base power influx system topology composition layered optimization design and an optimization design method thereof; the optimization design comprises two aspects: topology composition optimization design between the large-scale wind power base wind power plant and influx station and different voltage level influx stations; topology composition optimization design between internal wind power generators of the large-scale wind power base wind power plant and between the wind power generator and a transformer station; the optimization design method comprises the following steps: using an improved monolepsis algorithm to obtain an economic index Ctotal; using a Monte Carlo method to obtain a reliable index R; using min(OBJ)=[delta] 1Ctotal+[delta]2R as an evaluation rule to determine the power influx system topology composition according to the economic index and the reliable index, wherein the OBJ is the topology composition evaluation index, the Ctotal is the economic index, and the R is the reliable index.