The Lower Cambrian Longwangmiao grain beach sediments are of good potential of gas exploration in Sichuan basin. Based on the data from outcrops, cores and thin sections, and combined with the seismic interpretation, it is shown that the grain beach facies is composed of doloarenite, oolitic dolostone, crystalline grain dolostone and porphyritic dolostone in lithology. The grain beach facies includes three microfacies: the beach body, bank wings and beach flats microfacies. The reservoir mainly consists of the bank body microfacies. Grain beach contains multiple frequencies of shallowing-upward cycles. Each frequency of beach body is 2~20m in thickness and 0.9~1.5km in width. Multiphase beach bodies are superimposed to form a 18~55m thick, 7~8km wide and hundreds km long beach belt. The beach belt mainly develops in upheaval areas of the platform and distributes around the lagoon, which is controlled by ancient structures and sea-level changes. This viewpoint is useful to predicting the location of the Longwangmiao grain beach and helpful to improving the success rate of drills.