Hydrophobicity of poly(L-lactide) scaffolds is a main drawback in obtaining a sufficient mass of seeded cells for satisfying the requirements of tissue engineering. Plasma treatment is a useful technique to enhance the hydrophilicity of the scaffolds. However, the effect of this technique on the modifying depth and degradation of the scaffolds should be considered. In this paper, the influence of NH3 plasma treatment on the modifying depth and degradation of scaffolds were investigated. The results showed that the modifying depth of the scaffolds increased with treating time and the plasma power ranging from 20 to 80 W influenced the depth slightly. However, the degradation of the scaffolds increased with increasing treatment time and plasma power. The results also showed that the plasma intruded the scaffolds gradually from top to bottom. For a 4 mm thick scaffold, the optimized treatment condition was 20 W of power in a 30 Pa ammonia atmosphere for 30 min of treating time. Under this condition, the integrity of scaffold could be relatively well kept. NH3 plasma treatment enabled the penetration of cells into scaffolds and facilitated the proliferation of cells in them.