A probe cover for an ear thermometer and a grouping method of the same are provided. The probe cover for the ear thermometer includes a conical main body having a closed end and an open end, an annular elastomer, and a flange. The closed end is penetrable by infrared rays, and has different infrared transmittances according to thickness variations of the closed end. The annular elastomer is located between the conical main body and the flange. The flange has a plurality of detection positions, each of which having a positive detection pattern or a negative detection pattern, such that the detection positions are arranged to form a plurality of different detection combinations. The different detection combinations respectively correspond to the different infrared transmittances, and any two of the different detection combinations have the two corresponding infrared transmittances that are different from one another.