Experimental and numerical studies were conducted to understand flame extinction in SNG (synthetic natural gas)-air premixed flames with a counterflow configuration. The capability of some detailed reaction mechanisms in predicting flame extinction limit was evaluated through comparing predicted lean extinction boundaries with experimental ones. The results showed that those were best-fitted to numerical ones when the mechanism of UC San Diego was used and predicted flame locations were reasonably in agreement with experimental ones. Flame stability map was presented with a functional dependency on fuel volume fractions from lower and upper nozzles by varying global strain rate in interacting SNG -air premixed flames. Flame characteristics were identified to symmetric and asymmetric lean (rich)-lean (rich) flames and triple flames. The mechanism of flame extinction in interacting SNG-air premixed flames was explained and discussed by emphasizing important roles of downstream chemical interaction (via H-consumption) and upstream thermal interaction (via conductive heat loss to the ambience in the side of the stronger flame). Important role of H-radical (shared in downstream region) on chemical interaction was also discussed.