Abstract: Longwangmiao gas reservoir in Sichuan basin is the largest integrated marine carbonate gas reservoir in China. It is characterized by various types of reservoir spaces, strong heterogeneity, high background resisitivity, and strongly influenced by its lithology. So it is difficult to accurately calculate the gas saturation and identify the fluid types. This paper presents the array dielectric tool (ADT), a new dielectric log developed from Schlumberger, including the basic principle and the approach, and makes the exploratory studies of the pore structure, gas saturation and fluid property of this reservoir by means of the ADT-collected data from Longwangmiao gas reservoir, such as the dielectric constant, water-bearing porosity and the continuously variable cementation index (m) obtained by dielectric dispersion inversion. The results are in accordance with those from the semi-permeable barrier experiment of cores, the sealed coring and the oil production test