The 1.6 mm thick advanced high strength steel QP1180 was welded by an IPG YLS-6000 fiber laser. The effects of different heat inputs (14-36 J/mm) on the microstructure and properties of laser welded joints were investigated. The results show that the full penetration welded joint was obtained when the heat input reached 21 J/mm and above, and the width of fusion zone increased with the increase of heat input. There was a softened zone in the welded joints, but the degree of softening was low (≤10.1%). The softened zone was bound by the strengthening phase on both sides, leading to the fracture in the base metal, and the strength was equivalent to that of the base metal. In the Erichsen test, when the heat input was 21-36 J / mm, the cracking positions of the welding samples were perpendicular to the weld failure. The Erichsen values of three fully penetration welded joints all reached 70% of the base metal. The laser welding heat input range of 21-36 J/mm can ensure the full penetration weld seam performance meets the requirements of industrial applications.