Three methods (Box-counting method, The two-surface method and Berezovskava method) which were applied to estimate fractal dimension of poplar crown were compared in this study. The two-surface method was of heavy work and complexity. Berezovskava method was proved to be unsuitable for estimating fractal dimension of poplar crown due to its inaccuracy. In spite of limitation to 2-dimension, it is safe to say that Box-counting method was the best way to estimate fractal dimension of poplar crown owing to its easy operation, rapidity, high repetition, good stand for crown structure and foliage distribution. There was no link between fractal dimension of crown and crown shape, crown size, but a significant correlation was found between fractal dimension and foliage. Generally, the larger the foliage is, the bigger the fractal dimension is.