Post-tensioned prestressed hollow core slab is a common form of superstructure in bridge engineering. In this paper, the theoretical analysis of anchor stress in post-tensioned prestressed concrete hollow core slabs was carried out, and the effects of setting of reinforcement bars and thickness of web on anchor stress were discussed; the strain under anchor of hollow core slabs under the tension of steel beam was tested, and the cracks under anchor concrete were observed to analyze the mechanism of cracks under anchor. The study showed that: increasing the reinforcement rate of under-anchor reinforcement and thickening the web can reduce the under-anchor concrete tensile stress, and the effect of thickening the web is more significant; excessive local stress in the under-anchor concrete leads to local cracks and structural damage, and the cracks do not necessarily appear on the concrete surface immediately when the prestressing beam is tensioned, but appear after the stress redistribution in the under-anchor concrete.