Abstract: Following up the late progresses on deeply buried sandstone in overseas petroliferous basins, and based on the origin and controlled factors of anomalously high porosity in deep burial reservoirs, the authors discussed, taking the Chuanxi sag in Sichuan basin for the best scenario, that the preserving mechanisms of intergranular porosity in mid to deep burial sandstone intervals, and indicated that the primary conservation mechanisms of intergranular porosity in Shaximiao formation are as follows: development of chlorite coating, early petroleum emplacement and shallow development of fluid overpressure.