The utility model discloses a +/- 800kV ultra-high voltage direct-current line composite strain insulator string structure including a left yoke plate and a right yoke plate. A strain insulator string is arranged between the left yoke plate and the right yoke plate. A hardware fitting hanging point is further included. The strain insulator string is a composite strain insulator string. The strain insulator string adopts a quadruple square arrangement mode, wherein the pitch is 650mm. The utility model provides a +/- 800kV ultra-high voltage direct-current line 900/40 wire quadruple 550kN strain composite insulator string structure which can be used to improve the pollution prevention effect and has advantages of low production cost, convenient installation, reduced operation and maintenance cost and prominent economic benefits.