The invention discloses a target gene combination related to gestational age and application thereof. Based on the target gene combination, the target gene combination comprises TSPOAP1, CRYAA, CXCL11, FNDC10, HMGA2, FDCSP, OLFM2, KRT36, C13orf46, SCD5, OR12D2, OMP, CEBPE, MOBP, CCNF, FUT2, LIPH, ERICH4, GPR171 and the like. According to the method, the distribution condition of peripheral blood free DNA in some gene transcription start site areas can reflect different gestational weeks, and after the characteristics of the free DNA transcription start site areas are subjected to homogenization correction, a prediction model constructed by using a machine learning algorithm can effectively predict the fetal age of a fetus.