Laser filamentous wire additive manufacturing technology is a manufacturing technology that can rapidly form small parts. However, due to the influence of thermal accumulation effect in the manufacturing process, it is often unable to ensure the precision shape control of formed parts. In order to solve this problem, this paper uses the calibrated infrared thermography to collect the surface temperature of single pass multi-layer thin-walled parts, and studies the characteristic variation law of temperature field and heat accumulation effect in the manufacturing process, which provides a basis for the optimization of forming process. The results show that the infrared thermal thermography can be used to study the evolution of temperature field in the process of thin wall stacking. With the increase of cladding height, the area of high temperature area gradually increases, and the heat accumulation effect is significantly enhanced. In the process of cladding, the heat is conducted downward, the heat dissipation condition becomes worse gradually, and the cooling rate of each layer decreases with the increase of the number of layers until it becomes stable. In addition, when the number of cladding layers is more than 15, the thermal accumulation effect will no longer affect the cladding layers below 15.