In order to deal with the challenges in predicting the high cycle fatigue(HCF) crack initiation life of cast Al-Si alloy cylinder head，the impact of pore characteristics on the mechanical response of cast Al-Si alloy was investigated through a representative volume element model containing the pore. The relationship between pore size and the non-local maximum plastic shear strain amplitude p* max ? ? was established. The HCF strength of the cylinder head was evaluated based on the obtained model. The findings reveal a significant level of stress concentration at the local complex concave and convex positions of large pores. The harmfulness of pores is primarily determined by their size. With the increase in pore size， p* max ? ? experiences an accelerated growth. The HCF life of samples extracted from the cylinder head can be predicted within ±2.5 times dispersion band using the crack initiation model driven by p* max ? ? . The bottom plate，the inlet and the exhaust walls are the main parts of the cylinder head with high mechanical stress. The combination of high stress and large pores results in a low HCF life of the inlet wall.