The invention discloses a horizontal orientation method for advanced detection in a tunnel and belongs to the field of physical geography. Two 360-degree protractors having large areas are arranged on a base plate of a tunnel. An emission wireframe and a receiving wireframe are arranged right above the 360-degree protractors. After a zero-degree horizontal azimuth angle plane is determined, the emission wireframe and the receiving wireframe are rotated synchronously, and a horizontal azimuth angle and an angle plane thereof are determined according to an angle relation of orthographic projections of the emission wireframe and the receiving wireframe on the 360-degree protractors before and after rotation of the emission wireframe and the receiving wireframe. The horizontal orientation method for advanced detection in a tunnel is convenient for operation, has strong adaptability, is not influenced by an external environment, has high construction efficiency, adopts simple tools, improves work efficiency by above two times, has high orientation precision, eliminates personal factor influences, and has a low absolute error less than 5 degrees.