The invention discloses an intelligent material additive manufacturing device and method for a large steel truss. The manufacturing device comprises a mechanism part and a main body part. The mechanism part comprises a robot cantilever, a robot laser spray head, a robot rotary body part, robot mobile limbs and robot tentacles; and the rotary body part is controlled by the main body part and can rotate the cantilever flexibly and then adjust the angle and height of the laser spray head, the mobile limbs are connected with the main body part and the tentacles, and the mobile limbs are controlled by the main body part and drive the tentacles to move and then adjust the position of a robot. According to the intelligent material additive manufacturing method for the large steel truss, printed objects are utilized, limitation of an upholder is avoided, and three-dimensional printing in any space range can be achieved. In addition, an intelligent laser light source system is precise in positioning, has higher flexibility and is high in forming efficiency, and the forming difficulty of large objects is lowered.