The cutting fluid is widely used in cutting process with the cemented carbide tool. This paper studied the influence of some antirusting aggents, such as triethanolamine, tri-sodium phosphate, benzotriazole, sodium carbonate anhydrous, on the cobalt leaching of the cemented carbide tool by soaking test. The test results showed that a cobalt on cememted carbide surface and triethanolamine can produce complex compound into solution that made the cobalt leaching. The cobalt of the cemented carbide with the ion of the tri-Sodium phosphate in a water solution can form the loose deposition which leaded to the cobalt leaching.The benzotriazole and the cobalt can generate complex compound film covering on cemented carbide to effective inhibits the cobalt leaching. The inhibitive effect about the cobalt leaching of the sodium carbonate anhydrous is carried out through cathode reaction. The cobalt leaching of cemented carbide tool is effective inhibited by adding the benzotriazole and the carbonate anhydrous in the water-based cutting fluid.