In order to study the effect of influencing factors on the wave dissipation and figure out the optimized layout of wavebreak forest in the Nenjiang River mainstream, influencing factors including the arrangement mode, row spacing, stem radius, crown radius, width and rigidity were identified in this study. Then, the quantitative calculation and theoretical analysis based on the calculation formulas of wave dissipation performance were conducted for the Dongyang dike. The results indicate that the equilateral triangle is the best for the wave dissipation under the same trees; in the premise of not affecting the flood discharge, the dissipation effect is better when the forest stem radius, crown radius, and width is larger or the row spacing is smaller; the effect and duration of rigid vegetation is better than the flexible vegetation under a same width; a forest mainly consisting of the rigid vegetation and mixing with the flexible vegetation should be the optimized plan for the Dongyang dike, while the proper row spacing and width are 1. 5-2 m and 30-50 m, respectively. Besides, the flexible vegetation should be higher than the lowest top of rigid vegetation to achieve a better performance.