Aiming at the characteristics of the high building fire, setting the fire site scene, this paper carries out stage partition for fire on the angle of the countermeasure for fire, conducts accident analysis aiming at every stage applying FEA and ETA，finds out the related factors that affects fire development and stretch，and establishes the multiple-levels index system of high building fire hazard assessment. This index system can offer scientific basis for safe management of building, and can also lay the foundation for high building fire hazard assessment.