Mandelbrot enunciated the uncertainty of the length of a coastline in his paper “How long is the coastline of Britain？” published in “Science” in 1967. The fractal concept was presented for the first time in that paper and has been applied to many fields ever since. Although fractal dimensions of lots of phenomena were calculated, related studies on fractal character of drought and flood of China are seldom. Based on the fractal theory, issues of drought and flood were preliminarily discussed in this paper. Firstly, fractal structures of drought and flood were systemically analyzed to different regions and river basins; Secondly, changes of fractal dimensions of drought and flood with different grades and their relationships were also discussed as a case study of Tangshan city. Furthermore, quantitative experiential relationship between drought or flood and the influenced factor was established by use of the fractal dimension as a parameter. Some significant conclusions were drawn as follows：Fractal structure existed objectively in drought and flood of China, fractal dimension is a good parameter as a token of drought and flood. Moreover, the fractal dimensions of drought and flood of China were systematically calculated, and the change of fractal dimensions of drought and flood with different grades was analyzed, and the quantitative formula between the fractal dimensions of river basins and those of flood was established as D_F＝3.6179D_R－4.0242（where：D_R is the fractal dimension of river basin, D_F is the fractal dimension of flood）.