A study is made priliminarily in the paper on the fractal characteristics of size distributions of cities in Northeast China, and it is discovered that the city-size distribution of Liaoning Province has structure of bi-fractals, Jilin Province has single fractal patterns, and Helongjiang Province has a local fractal feature.As for the whole region including the three provinces, it has a local fractal pattern with some sign of bi-fractals.Zipf dimensions of every system of cities is calculated and the corresponding fractal dimensions are estimated.Some proposals based on fractal idea are put forward to optimize the rank size distribution and hierarchy of urban systems in Northeast China, and some theoretical and practical benefits can be gained from this study that ① The fractals of city-size distributions are not only a kind of form and structure, but also a process, they can change from one pattern to another:local fractal, bi-fractals, and single fractal, ortransfer in inverse direction;② Geographical fractal theory can be used to optimize city-size distribution in a region in place of some simple city-size policy such as ‘strictly control sizes of large cities, rationally develop medium sized cities, and actively develop small cities and towns’, which as a typical ‘schemic design’ is not only invalid but also dangerous in practice.