Based on terrain elevation isolines from topographic maps with scale 1:50 000 and 1:1 000 000 in Tianshan area in Xinjiang, the fractal dimensions of isolines in 6 studying sectors from 3 different types of geomorphology, including high mountain, low -moderate mountain and catchment basin, are computed by using successive coarsening method. The results show that all the studied isolines are statistical fractals, and the fractal dimensions take on different characters for different geomorphological regions and scale ranges. It can be inferred that the fractional dimension values are closely dependent on the erosional intensities, and it can be a very important parameter in geomorphological and geodynamic researches.