The average temperature of Gasi E31 reservoir is 126 °C, the total salinity of formation water is as high as 18 × 104mg/L, and the conventional water plugging agent is easy to degrade or dehydrate and break rubber under high temperature and high salt conditions, resulting in the decrease of effective plugging and poor long-term stability. A temperature-resistant and salt-resistant organic water-plugging system composed of temperature-resistant and salt-resistant polymer, phenolic crosslinking agent, chemical additives and oxygen scavenger was developed, based on the principle of molecular structure design. Meanwhile, the temperature-controlled gel inorganic water plugging system was selected, and a composite water plugging system of “gel + gel” suitable for high-temperature and high-salt reservoirs was initially formed. The laboratory test results indicated that the plugging rate of the composite system could reach more than 91% under high temperature and high salt conditions, and the dehydration rate of the system could reach more than 85% after 60 days of aging. The laboratory test results indicated that the plugging rate of the composite system could reach more than 91% under high temperature and high salt conditions, and the dehydration rate of the system could reach more than 85% after 60 days of aging. The field test of one well was carried out on site. The pressure drop curve was significantly slowed down after water plugging, which proved that the dominant channel was effectively blocked, the water cut decreased from 99 to 81%, and the daily oil production increased from 0.07 to 0.85t. The research results show that the “gel + gel” compound water plugging system has a significantly effect on the precipitation and oil increase in Gasi E31 reservoir, and the success of the well water plugging marks a breakthrough in the water plugging process of high temperature and high salt reservoir in Qinghai oilfield, which provides a strong technical support for the treatment of high water content Wells in Gai deep layer in the next step, and has a good promotion value.