This article presents the design of a spaceborne line laser capable of projecting a single line shape for in-orbit measurement of thermal deformations on the surfaces of synthetic aperture radar antenna arrays. The laser incorporates a heat dissipation structure and adheres to resistance theory, making it suitable for the rigorous thermal vacuum environments encountered in space. Its beam width remains under 3 mm at a distance of 4.5 m, and the directional shift following continuous operation for 5 min is less than 25 μrad. Functioning effectively within a temperature range of 0?30 ℃, the laser exhibits high flatness, broad coverage, and remarkable stability. This design offers a novel technical reference for future in-orbit measurements of large-scale structural deformations.