The dome building eruption of Unzen Volcano (1990-1995) displayed destructive aspects of Pyroclastic flows. The eruption resulted in the deaths of 44 people by pyroclastic surge. It is one of the most important problem to predict the risk from surges for hazard assessment. This study focuses on the impacts of surges and human injurer. A detailed analysis of the distribution and damaged houses of the surges on June 3, 1991 was used to study on the characteristics of surges. The result revealed that human injurer related the topographic effects of pyroclastic surge. Flow direction of the surge based on damaged trees and houses show a straight pattern from the Mizunashi River. But the direction changed a little after contact of mound of Mt Mayu. It is important study for future implication for volcanic hazard assessment.