The invention discloses an epitaxial technique for filling a high aspect ratio groove, comprising the following steps: carrying out epitaxial growth on a substrate silicon sheet to form an epitaxial layer; photoetching a groove on the epitaxial layer for the first time; etching the groove, wherein, the etching depth of the groove achieves the maximum depth needed in the technique; coating chemical filling materials in the groove, wherein, the filling depth is more than or equal to the depth of the groove; etching the chemical filling materials, wherein, the etching depth is equivalent to the depth of the groove etched for the second time; photoetching the groove for the second time, wherein, the groove width photoetched for the second time is more than the groove width photoetched for thefirst time; etching the groove for the second time so as to form a stepped groove structure, wherein the etching depth is determined according to the requirements of the technique; removing the chemical filling materials in the groove; and carrying out N-type epitaxial growth in the groove; and filling the groove. By utilizing the technique provided by the invention, the position at which a cavity appears can be effectively controlled, and even the cavity is ensured to disappear.