The invention discloses a horizontal well completion pipe string guide resistance reducing device and relates to supporting tools for well-completion practice pipe strings in oilfield development. The horizontal well completion pipe string guide resistance reducing device is used for guiding a well completion pipe string to go down to a well. The upper portion outside a center pipe (2) is sleeved with a spring (3). The lower portion outside the center pipe (2) is sleeved with a rotary inner sleeve (5). A torsional mechanism is arranged between the center pipe (2) and the rotary inner sleeve (5) and in the middle of the outer wall of the center pipe (2). The outer wall of the rotary inner sleeve (5) is provided with an inclined groove. The lower end of the center pipe (2) is connected with a ball seat (7) and a pressing cap (8). The rotary inner sleeve (5) is sleeved with a rotary outer sleeve (4). The inner end of a guide block (6) extends into the inclined groove of the rotary inner sleeve (5). The upper portion of the rotary outer sleeve (4) is in a cylindrical shape and is provided with an inclined protrusion, and the lower portion of the rotary outer sleeve (4) is in a conical shape. A spherical part of a spherical head (9) is installed in a semispherical inner groove formed by the ball seat (7) and the pressing cap (8). The lower portion of the spherical head (9) is connected with a guide head (10). Due to the fact that the horizontal well completion pipe string guide resistance reducing device can drill and mill a well and adopts a universal joint structure, the well completion pipe string can go down to the well more easily.