Cutting fluid is the essential material in metal cutting process. This paper mainly studies the influence of TEA-containing solution on cobalt leaching from cemented carbide tools and the leaching mechanism, and then identifies the effective inhibitor. The results are as follows: (1) TEA additive can make cobalt leach from cemented carbide tools. (2) Addictive of triethanolamine oleate in the solution can obviously inhibit the leaching of cobalt from cemented carbide tools and there exists the best proportion. (3) The mixture of triethanolamine oleate and borax has the best inhibition function. So it can conclude: The mixture of triethanolamine oleate and borax can obviously reduce the leaching of cobalt from the cemented carbide tools, which improves the working life of the cutter and reduces the danger of the fluid to human body.