Abstract: A model to analyze forces on deadman in a hearth under a special condition was constructed and a method to calculate the minimum depth of salamander was put forward. Proved by data from a dissected blast furnace (BF), the calculation method was perfect. On the base of the former model, a new model for deadman force analysis on the general condition was built, a reliable formula to estimate the height of deadman floating was deduced, and the relationship between deadman floating height and liquid slag surface was discussed.