Based on the analysis of rock types, fossils, sedimentary texture and sedimentary facies from rock cores, sections and logging data, it is suggested that the Lower Triassic Jialingjiang 2nd Member deposited in the environments of restricted sea and evaporation platforms in the northeast part of Sichuan basin, which is characteristics of platform flat, tidal flat and calcarenite bank subfacies. It has experienced an entire transgression-regression cycles from the supratidal evaporation environment (evaporation tidal flat) pass the low-energy subtidal environment (dolostone flat and limestone flat) then to another supratidal evaporation environment (evaporation tidal flat). It is suggested that calcarenite bank, dolostone flat and limestone flat developing in the relatively low energy environment are the reservoirs most favorable for hydrocarbon accumulation.