Abstract: Suicide is not only a problem in the field of forensic medicine,but also a problem of sociology.In this paper,the causes of suicide based on the data collected from certain area in Shanghai had been analysed.It is recognized from the results analysed that in one hand,in the prevention point of view,chemical intake,especially pesticides and sedatives,was the most popular(67.8％)way of suicide in this area,and on the other hand, there were 51 cases in which the intention of suicide had been discovered and stoped.So in the work of prevention,it is suggested that the passive way we may take is mainly to control chemicals and the positive way is to discover the intention of suicide and stop it in time.In the paper,other types of suicide method have also been discussed.