In the mining system of potassium salt mine of Ganmeng Province in Laos, the ventilating shaft passes through carnallite and halilith, which are easily soluble in water. After the ventilating shaft excavating, cavern phenomenon, a serious threat to the normal function of the shaft, is found behind shaft wall. In order to ensure the safety of shaft construction and the normal production, curtain grouting is adopted to control the disease of ventilating shaft. The closed curtain grouting technology is adopted with the method of grouting from the top to bottom and with effect checking while grouting to finish the reinforcement and water plugging. The cementing materials used for carnallite and halite layer were tested in laboratory, a new type of grouting material, brine + magnesium oxide slurry was determined together with the scientific grouting mix ratio. By the summarization, the design and construction experiences are accumulated for waterproofing and water blocking in potash mine mining process.