Dengying formation gas reservoir in Anyue Gas Field, which is a low permeable dolomite reservoir and buried at depth of 4000–5000 m. The reservoir has strong heterogeneity and is mainly developed by highly deviated wells and horizontal wells. These wells were typically stimulated by acid fracturing with large-scale. The gas wells showed high fracture conductivity and high initial gas productivity, but some wells experienced a rapid decline in productivity after several months of production, both the BHP and tubing pressure dropped significantly with great fluctuation. The study was undertaken to identify the key factors on the productivity loss. A series of experiments, such as X-ray diffraction, acid dissolution, SEM with EDS, were carried out. Combined with sedimentary characterization, study of acid-rock reaction mechanism and analysis of well performance, the cause of blockage were confirmed. The solid plugging material is mixture of pyrolysis asphalt, quartz and mud particles with over 60% insoluble to acid, and the blockage was mainly occurred during the process of stimulation, well control, corrosion inhibitor and antifreeze injection. The blockage occurred in the gathering and transportation system could be eliminated by organic solvents with acid, but the blockage in near wellbore formation is very difficult to remove. The solid particles of asphalt, quartz came from dolomite reservoir which is undissolved by acid. Therefore, reducing the volume of acid fluid during acid fracturing treatment will be benefit for preventing near-wellbore blockage. This research has gathered valuable information on cause of gas well blocking and provide better understanding on reducing and removing blockage for new gas wells in the Dengying formation gas reservoir and similar assets.