Abstract: The relationships between understory vegetation coverage and environmental factors in Pinus massoniana plantations from aerial seeding were studied by using principal component analysis, redundancy analysis and variation partitioning. The selected environmental factors in total explained 74.2% variation of the understory vegetation coverage. At low altitude, stand characteristics were the key factor to influence the understory vegetation coverage. Stand characteristics, soil property and topographic factor were respectively explained 55.0% (including 29.1% for separateness and 25.9% for interaction with other factors), 38.9% (including 12.1% for separateness and 26.8% for interaction with other factors) and 9.0% (including 5.6% for separateness and 3.4% for interaction with other factors) of the total variation. Average diameter at breast height and canopy density affected mostly and positively correlated with the coverage of bryophyta, graminoid and shurb groups at significant level. Noncapillary porosity and soil water content showed a highly significant positive correlation to dicranopteris coverage, whereas average diameter at breast height, canopy density, soil nutrients and enzyme activity significantly negatively correlated with it. The coverage of graminoid, bryophyta and shurb groups showed the positive correlations, which indicated the three groups could promote each other, while the dicranopteris coverage had significant negative correlation with the three groups mentioned above.