The invention discloses a big arm of a robot, and the robot. The big arm of the robot comprises a main arm body, a first connecting part and a second connecting part, wherein the main arm body has a preset length and a preset thickness, and the first connecting part and the second connecting part are located at the two ends, in the length direction, of the main arm body correspondingly; a groove which extends in the length direction of the main arm body and is concave in the thickness direction of the main arm body is formed in the main arm body; and the groove comprises a bottom wall, a first side wall, a second side wall, a first end wall and a second end wall, the first side wall and the second side wall are located on two long sides of the bottom wall, and the first end wall and the second end wall are located on two short sides of the bottom wall. Two or more reinforcing ribs are arranged in the groove in the mode of a preset pattern and used for improving the strength of the big arm of the robot. At least one of the reinforcing ribs is provided with a wiring hole and / or wiring slot allowing a cable to penetrate through, and the cable can penetrate through the groove in the length direction of the big arm through the wiring hole and / or the wiring groove.