The present invention relates to a lightningproof anti-ice-flashover composite insulator for a 500kV line, which is characterized in that the composite insulator successively comprises an upper unit part, an upper grading ring, a lower unit part and a lower grading ring from top to bottom. The upper grading ring is mounted on an upper end of the lower unit part; the lower grading ring is mounted on a lower end of the lower unit part; the upper unit part comprises a lightning arrester and a first sub-insulator in parallel; the lower unit part comprises a second sub-insulator and a third sub-insulator in parallel; an upper end of the second sub-insulator is connected with a lower end of the first sub-insulator; and an upper end of the third sub-insulator is connected with a lower end of thelightning arrester. The composite insulator improves the lightning protection and anti-ice-flashover capability of the 500kV composite insulator.