A method for analyzing light n-alkane components and carbon isotopes in deep and ultra-deep source rocks includes: (S1) subjecting a 5A molecular sieve column to aging; (S2) pyrolyzing a source rock; and allowing a pyrolysis product to enter the 5A molecular sieve column; where n-alkanes are adsorbed and retained by the 5A molecular sieve column; allowing an outflow to pass through a fractionation plate and an empty column or a weak polarity column to be discharged; and (S3) performing programmed heating such that the n-alkanes adsorbed on the 5A molecular sieve column are successively desorbed according to molecular weight, and then pass through the fractionation plate and the HP-5 or DB-5 column to enter a mass spectrometer for composition analysis or isotopic analysis. An analysis system is further provided.