The invention relates to a seven-freedom-degree five-finger mechanical arm, and belongs to the technical field of robots. The mechanical arm comprises a palm, five fingers, seven motors, a drive gear, a driven gear, a transmission shaft, a drive steel wire rope, a driven steel wire rope, three pairs of worm wheels, a worm, a hoop and a rolling cylinder. Any of the index finger, the middle finger, the third finger and the little finger has one bending freedom degree, the index finger, the third finger and the little finger have one swing freedom degree so that the three fingers can be unfolded or folded at the same time, the thumb has one bending freedom degree and one swing freedom degree, and the seven freedom degrees are set. By means of the seven-freedom-degree five-finger mechanical arm, bidirectional bending of the five mechanical fingers can be achieved, the index finger, the third finger and the little finger can be folded and unfolded, bidirectional swing of the thumb is achieved, and a precise grabbing task can be completed.