The safety block which prevents drop of laborers at high altitude was analyzed by finite element method. Elastic analysis was done by Ansys ver. 11.0. and tetrahedral meshing was used. As load applied more vertically at the fixed face of saw tooth, the stress concentration became smaller and the load distributed broader. When load worked at saw tooth and the shape was more straight to the direction of load, most stresses except principal stress became smaller. When the area of the load increased, principal stress and equivalent stress could be decreased simultaneously. A principal stress and other various stresses occurred in 3D shape, therefore revised model which has smaller equivalent stress than other models shows excellence on the stability and the credibility.