An architectural optical assembly used for receiving light beam (10, 30), and comprising: a discolorable element, used for receiving the light beam (10, 30) to exhibit discoloration effect; and a light-shielding element, disposed adjacent to the discolorable element and used for shielding a part of the light beam (10, 30) having a wavelength within a predetermined range; characterized in that said assembly further comprises a light-guiding film, wherein the light-guiding film comprises: a film base, having a first side and a second side opposite the first side; and at least one microstructure, disposed on the first side or the second side of the film base, and having a first surface and a second surface above the first surface, wherein a first inclination angle (θ 1) is between the first surface and a reference plane, the reference plane is perpendicular to the film base, a second inclination angle (θ 2) is between the second surface and the reference plane; whereby a plurality of incident light beams becomes a plurality of output light beams after passing through the light-guiding film, an output angle (θ 3) is defined as the angle between the output light beam and the light-guiding film, the output angle (θ 3) is defined as 0 degree when the output light beam is downward and parallel with the light-guiding film, the output angle (θ 3) is defined as 180 degrees when the output light beam is upward and parallel with the light-guiding film, the total luminous flux of the output light beams with the output angles (θ 3) from 85 to 120 degrees is more than 40% of the total luminous flux of the output light beams with the output angles (θ 3) from 0 to 180 degrees. a discolorable element, used for receiving the light beam (10, 30) to exhibit discoloration effect; and a light-shielding element, disposed adjacent to the discolorable element and used for shielding a part of the light beam (10, 30) having a wavelength within a predetermined range; characterized in that said assembly further comprises a light-guiding film, wherein the light-guiding film comprises: a film base, having a first side and a second side opposite the first side; and at least one microstructure, disposed on the first side or the second side of the film base, and having a first surface and a second surface above the first surface, wherein a first inclination angle (θ 1) is between the first surface and a reference plane, the reference plane is perpendicular to the film base, a second inclination angle (θ 2) is between the second surface and the reference plane; whereby a plurality of incident light beams becomes a plurality of output light beams after passing through the light-guiding film, an output angle (θ 3) is defined as the angle between the output light beam and the light-guiding film, the output angle (θ 3) is defined as 0 degree when the output light beam is downward and parallel with the light-guiding film, the output angle (θ 3) is defined as 180 degrees when the output light beam is upward and parallel with the light-guiding film, the total luminous flux of the output light beams with the output angles (θ 3) from 85 to 120 degrees is more than 40% of the total luminous flux of the output light beams with the output angles (θ 3) from 0 to 180 degrees. a film base, having a first side and a second side opposite the first side; and at least one microstructure, disposed on the first side or the second side of the film base, and having a first surface and a second surface above the first surface, wherein a first inclination angle (θ 1) is between the first surface and a reference plane, the reference plane is perpendicular to the film base, a second inclination angle (θ 2) is between the second surface and the reference plane; whereby a plurality of incident light beams becomes a plurality of output light beams after passing through the light-guiding film, an output angle (θ 3) is defined as the angle between the output light beam and the light-guiding film, the output angle (θ 3) is defined as 0 degree when the output light beam is downward and parallel with the light-guiding film, the output angle (θ 3) is defined as 180 degrees when the output light beam is upward and parallel with the light-guiding film, the total luminous flux of the output light beams with the output angles (θ 3) from 85 to 120 degrees is more than 40% of the total luminous flux of the output light beams with the output angles (θ 3) from 0 to 180 degrees.