The carbon steel samples of great quality can not be melted using a high-temperature confocal scanning laser microscopy(HTCSLM). On account of only arc surface of the tiny liquid-drop top is observed, it is difficult to obtain distinct images. The shape variation of the tiny liquid-drop is studied experimentally in this article. The results show that the shape of the liquid-drop will be changed at 1600°C, when the carbon steel sample of 0.5g is laid on the Al2O3 sloping of 15 degrees. Though the radius of curvature of the liquid-drop top surface is obviously enlarged, the impact of improving the surface shape of liquid-drop through the gravity flow of tiny liquid-drop is finite. For the carbon steel sample of less than 0.8g, the hanging drop is automatically formed in the melting process under the condition that the gap between the solid sample and Al2O3 single crystal plate is 0.3mm, and the shape retains invariant when it is hold for 20 min at 1600°C. The contact surface between the sample and Al2O3 single crystal plate is 24mm2.