Abstract: Objective The aim is to investigate the influence of adhesive layer addition on welding temperature and joint internal forming of friction stir lap welding process. Methods Taking 3 mm-thick 2024-T4 aluminum alloy as the object, temperature field was subjected to finite element simulation through MSC.Marc software and verified through the temperature measurement test of K-type thermocouple. Welding temperature distribution of friction stir lap welding and friction stir lap welding bonding process and the internal forming characteristics of the joints under the influence were compared and analyzed. Results The adhesive layer added at the lap interface has a smaller thermal conductivity than that of aluminum alloy, which makes peak temperature of the upper plate higher and high-temperature zone larger, resulting in a wider stir zone of the upper plate, and an increase in the length and height of the cold lap extending into the stir zone. Conclusion Compared with friction stir lap welding, high-temperature zone of the lower plate of friction stir lap welding bonding process is smaller, which makes the hook bend downward and has a larger bending angle in the lower plate. The average tensile shear property of the joints is increased from 12.14 kN to 14.34 kN.