Abstract: In the West Sichuan Depression with tight sand,the formation mechanism of traps and gas reservoir is quite complicated,resulted from the basin's complex evolution.Even in different structural part or horizon of the same structural deformation band,there exists distinct difference in both oil-and-gas bearing condition and geological factors restricting trap and gas enrichment.There are structural traps where structural activities enrich oil and gas.There are also non-structural stratum and lithologic traps,such as palaeostructural-lithologic trap,palaeostructural-diagenetic trap,and structural-lithologic trap,where structural activities cooperate with lithology,lithofacies,and sedimentary environment.