Abstract: By controlling the pouring temperature and increasing the flow agent test, the influence of the two factors on the cylinder head leakage of a high-speed machine was verified, the method to prevent the leakage of the cylinder head of this high-speed machine was found. The test finds that, when the starting pouring temperature is 1389 ℃and the minimum temperature is not lower than 1351 ℃, the cylinder head castings with dense microstructure can be obtained, the leakage defect of this type of cylinder head can be eliminated. The addition of 0.1% in-flow inoculant can also effectively solve the leakage phenomenon of the cylinder head. However, after increasing the test pressure and extending the pressure retention time, there is also a leakage phenomenon. Therefore, it is more effective to increase the pouring temperature than adding in-flow inoculant to prevent the leakage of the cylinder head of the high-speed machine.