The oil pan is one of the main diesel engine components that makes radiated noise. The key to reducing overall engine noise is controlling and reducing the radiated noise level of the oil pan in the design stage. In order to effectively do so, the vibration and radiated noise of the original oil pan is estimated and predicted, and the following structure optimization approach is proposed accordingly. Firstly, the noise prediction model of the original oil pan is built up. Secondly, the main peak frequencies are found according to the prediction results and used in combination with the oil pan natural frequency. The overall objective is to reduce the overall radiated noise of the oil pan, and the sub goal is to reduce the main peak of the noise spectrum. Lastly, a multi-objective optimization function is built in order to begin structure topography optimization. The results show that overall noise is reduced 2.79 dB compared to the original overall sound pressure level of 100.23 dB, through appropriate arrangement of the stamping ribs. This optimization scheme can decrease the repetition and subjectivity of the process design test-improved design, reducing the design cost and shortening the design cycle.