The invention relates to a torsion impactor for well drilling and a method. According to the technical scheme, the torsion impactor for well drilling is characterized in that a filter screen is arranged on the lower portion of the inner side of an upper connector; an upper disc piece is arranged in the connection position of the upper connector and an outer cylinder; two valve holes A are formed in the upper disc piece; a central hole is formed in the inner side of the outer cylinder; an impact block is arranged on the outer side of the central hole; an impact block bottom bearing piece is arranged at the bottom of the impact block; a fixing valve block is arranged on the outer side of the impact block; a lower disc piece is arranged on the lower portion of the impact block bottom bearingpiece; an inlet disc piece is arranged on the upper portion of the fixing valve block; the two sides of the inlet disc piece are arranged symmetrically; two liquid guiding holes, namely the first liquid guiding hole B and the second liquid guiding hole C, are formed in the two sides of the inlet disc piece correspondingly; and four elliptical pressure relief holes are formed in the lower disc piece. The torsion impactor has the beneficial effects that high-frequency torsion impact of a drill bit is achieved through a mode of impacting a tool body directly; and an impact hammer directly acts onthe drilling tool body, so that the structure is simpler, using is more reliable, and the life is prolonged greatly.