During experimental period, Wudu, in Zhouqu and Wenxian Counties, there had been forecasted 16 times of disaster Successfully and prevented 7021 peoples from injury and death, and reduced the loss of property being equal to 20761500 Chinese Yuan. The ratio between input and benefit is 1:8.65. At the same time, 75 dangerous places of landslide and debris flow were treated in time to ensure 73677 people's life and the property valued 255092000 Yuan safety in the risk area. It is showed that mass monitoring and mass preventing are low cost and high benefit. Through these triales, it not only lowered the degree of the loss on disaster in mountainous area to be smallest, but also probed into the method, accumulated the experiences, and found the way of disaster prevention and reduction, which depends on the station of forecast and warning, which takes mass monitoring and mass preventing as foundation of landslide and debris flow forecasting and warning. It laid a good foundation for popularizing mass monitoring and mass preventing on a large scale.