Abstract: From the view point of system of natural disasters, some features of this system are described, a new concept of the complexity of natural disasters is put forward. On the basis of some research achievements in natural disasters, the application of fractal dimension and chaos, artificial neural network,as well as the comprehensive technology with qualitative and quantitative integration to the study on the complexity of natural disasters are discussed. Through the study on the complexity of natural disasters, the process of investigation on the whole behaviour of natural disasters will get a promotion.