The object of research is detecting and eliminating the unsafty factor in shortest time through a decision making simulation under uncertainty using simulation method The decision making simulation using C language Is used to analyze data from several factors which affects the crane breakdown under unsafe situation. Through this research, the following conclusions are obtained. first, the safety manager or the person can estimate the time required to handle the unsafe factors. Secondly, The decision making can be accomplished by minimizing the time required under uncertainty by analyzing them.