The Marangoni effect caused by the temperature gradient often causes molten pool overflow on the smoothed surface, which reduces the effectiveness of continuous laser polishing of metal surfaces. To reduce the Marangoni effect in the laser polishing process, 304 stainless steel substrate was heated to reduce the molten pool temperature gradient. The substrate temperatures are 25, 100, 200, and 300 ℃ respectively. Surface roughness, the cross-section of molten pool, and surface micromorphological features of laser polishing specimen were measured and analyzed by laser scanning confocal microscope and scanning electron microscope. The experimental results indicate that a smother laser polishing surface can be obtained by heating the substrate surface compared with room temperature polishing. With the increase of substrate temperature, the width and depth of the molten pool increase, and the ratio of depth to width increases. When the substrate temperature is 100 ℃, laser polishing could enable reductions in surface roughness of over 75.9% (from 1.08 μm to 0.26 μm Sa) while also eliminated the machining marks originally on the specimen. The carbide precipitation on the polished surface increases and the step structure is enhanced when substrate temperature increases.