In order to approach the impact of understory vegetation structure on growth of Polygonatum cyrtonema and establish a theoretical basis for compound management of it in Phyllostachys edulis plantation, The different species composition, physical characteristics and distribution patterns of the understory plants at semi-shady lower slope in extensively managed Phyllostachys edulis plantation were studied. For the research both coorelation and principal analyses to examine diversity indexes of the understory plants with growth indexes of P. cyrtonema were employed. The results are as the following: (1) 34 species belong to 27 families and 32 genera which are recorded in the test plots of Ph. edulis plantation. In particularly, Litsea cubeba, Rubus corchorifolius, Phaenosperma globosa, Miscanthus floridulu, Dicranopteris dichotoma and P.cyrtonema are dominant species within understory plants. (2) The spatial distribution pattern of P. cyrtonema is variously distributed,whereas the others’ species are distributed clumped. Meanwhile, the clump intensity of these species is illustrated as descending order: M. floridulu > D. dichotoma > P. globosa > L. cubeba > R. corchorifolius. (3) There is significant (P < 0.05) or obvious significant (P < 0.01) correlation among P. cyrtonema growth indexes with abundance, height and diversity indexes of the understory plants in Ph. edulis plantation. Especially, Shannon-Wiener diversity index (H) and containing absolute abundance diversity index (I) are the major impact indicators. Furthermore,P. cyrtonema grows well when H is indicated between 0.2924-1.2049 and I is indicated between 2.8439-8.8099. (4) Therefore, to promote P. cyrtonema growing well in Ph. edulis plantation, the abundance of the understory plants should be controlled in-between 159 and 843 ind/m² by hilltops weeding in September and October.