The invention relates to the technical field of engine casting, and in particular relates to a core assembly bonding process and a core assembling method for a sand core of a cylinder cover with the process. The core assembly bonding process comprises the following steps: S1, forming a penetrating injecting hole for injecting a hot melt adhesive in a bonding sand core; S2, coating the face, which is in contact with the bonding sand core, of a sand core to be bonded with an adhesive; S3, placing the bonding sand core on the sand core to be bonded; S4, injecting the hot melt adhesive into the injecting hole of the bonding sand core. By the adoption of a 'hot melt adhesive + adhesive' bonding method, the hot melt adhesive is injected through the injecting hole to quickly bond the bonding sand core and the sand core to be bonded; therefore, under the condition of ensuring that the bonding sand core and the sand core to be bonded can be quickly and fixedly bonded, the use amount of the adhesive can be greatly reduced, so that the gas generating amount is reduced, and casting pitting defects can be reduced favorably; the hot melt adhesive is basically volatilized in a drying process, so that core assembly bonding materials are reduced, defective products in a core assembly pouring process are reduced, and control over an on-site process and quality improvement can be facilitated.