The invention discloses a method for aided identification of fat tail properties of sheep and a special molecular marker used therein. The invention provides the method used for aided identification of fat tail properties of a to-be-detected sheep colony. The method comprises the following steps: (1) randomly drawing a to-be-detected sample with statistical significance from the to-be-detected sheep colony; (2) detecting the T/C ratio of site 59383635 of an X chromosome of the to-be-detected sample; and (3) carrying out evaluation according to the standards that the to-be-detected sheep colony is a fat rump type colony if the T/C ratio is greater than 5, the to-be-detected sheep colony is a slim tail type colony if the T/C ratio is smaller than 0.5 and the to-be-detected sheep colony is a short fat tail type colony if the T/C ratio is in a range of 1 to 2. Experimental results of the invention show that distribution of the site 59383635 of the X chromosome of sheep in a fat tail (rump) type sheep colony and a slim tail type sheep colony is greatly different and the SNP site can be used as an ideal molecular marker for breeding of a low fat sheep variety.