The utility model discloses a fixture for replacing an end strain insulator string on a 800kV line, which comprises a front fixture (5), a rear fixture (1) and two groups of retraction components of which the two ends are respectively articulated with at the two ends of the front fixture and the rear fixture, wherein the front fixture (5) is an integral component which consists of a front fixture body (51) and a turn-over cover (52) articulated with the body, a mould cavity (53) at the middle part of the front fixture (5) is matched with the surface shape of a twin bowl head (7) of line hardware, and the mould cavity at the middle part of the rear fixture (1) is matched with the surface shape of a drawing plate (8) of the line hardware. During the replacing the end strain insulator string, the mould cavity (53) of the front fixture is locked with the twin bowl head (7) of the line hardware in a matching way, the mould cavity of the rear fixture (1) is matched with the drawing plate (8) of the line hardware and locked through a bolt, and the replacement of the whole end strain insulator string can be implemented by operating the retraction components. The fixture has the advantages that the operation is convenient, safe and stable, thereby being very suitable for the replacement of the end strain insulator string on the 800kV extra-high-voltage transmission line.