Abstract: The containment failure by melt-through during severe accident is analyzed and calculated based on the contact melting around the heat source. A new and more rational analysis model of contact melting is established under certain hypothesis,and the melting velocity and the time needed for melt-through are calculated. The results are compared with some related literatures. The mass of heat source and the heat transfer ratio k as the main factor on melt-through are analyzed,and the conclusions are drawn that the melting velocity is in direct ratio with the mass of heat source and approximately in direct ratio with the heat transfer ratio,and however the relation of the time needed for melt-through with the mass of heat source and k is in the opposite way. It is indicated that in order to delay the melt-through additional engineering device to reduce the mass of single heat source and enhance the upside heat transfer is of great importance.