Al-Cu alloy with wide solidification interval is prone to hot tearing and porosity defects due to insufficient feeding. The effect of hydrogen content on the hot tearing susceptibility (HTS) of Al-xCu alloy was investigated by the constrained rod casting (CRC) mold. Based on analysis of the HTS value, fracture morphology and the microstructure of Al-xCu alloy with different hydrogen contents in the melt, the influence of porosity formation on the hot tearing was analyzed. The results show that the hot tearing susceptibility of the alloy is evidently aggravated, which is caused by grain coarsening and insufficient feeding of liquid phase in the late stage of solidification with the increase in melt hydrogen content. A porosity-based formation mechanism of hot tearing is proposed to explain the interplay between porosity and hot tearing.