The invention discloses a precision outer supporting type chuck. The precision outer supporting type chuck comprises a machine platform mandril, a supporting chassis and a cylindrical chuck body which is arranged at the center of the top of the supporting chassis. The precision outer supporting type chuck is characterized in that protrusions are arranged on the side face of the chuck body to vertically divide the supporting chassis and the chuck body into a plurality of single bodies by using the center of the circle of the supporting chassis as the center, gaps are arranged between the single bodies, the center of the bottom of the supporting chassis is provided with an annular connector which is connected with all the divided single bodies of the supporting chassis, the machine platform mandril is inserted into the annular connector, and when the machine platform mandril applies force on the supporting chassis, the divided single bodies of the chuck body are deformed from inside to outside to fix the inside of a product to be processed. The appearance of products is prevented from being damaged, and the precision outer supporting type chuck can be used for processing the products which have high requirements for appearance.