Separation of light hydrocarbon mixtures and extraction of C3H8 and C2H6 from CH4 are of significant importance in natural gas purification and upgrade. Microporous carbon adsorbents are promising in light hydrocarbons separation, but to fabricate uniform ultramicropores to boost separation selectivity remains challenging. Herein, we fabricated a series of poly(vinylidene chloride) resins-derived ultramicroporous carbon adsorbents with relatively uniform pore size (5.2-5.3 Å) by activator-free pyrolysis. The optimal C-PVDC-800 exhibited record-high IAST selectivity of C3H8/CH4 (3387) and C2H6/CH4 (75) as well as Henry’s selectivity of C3H8/CH4 (369) among all reported adsorbents under ambient conditions, combined with ultrahigh uptake of C3H8 (3.9 mmol g-1, 0.05 bar) and C2H6 (2.67 mmol g-1, 0.10 bar) at low partial pressures and 298 K. More importantly, fast gas adsorption kinetics were realized, favorable in fixed-bed adsorption applications. Breakthrough experiments and cycling tests further confirm the superb separation performance of extraction of C3H8 and C2H6 from CH4.