Abstract: The forest gap and the plant diversity in Larix kaempferi plantation was investigated by plot method in Changlinggang Stateowned Forest Farm of Jianshi county in western Hubei. The influence of gap disturbance over plant diversity in Larix kaempferi plantation Was analyzed by 4 biodiversity indexs. The results showed that species amounts of woody plants and herbs，Shannonwiener index and Simpson index were significantly higher than the nongap ones. Pielou index was also slightly higher than it;Within forest gaps of varied scale， it presented a pattern of plant diversity that in middlesize gap(50~100 m2)＞smallsize gap（＜ 50 m2）＞largesize gap（＞100 m2）. Species diversity in forest gaps was higher than in nongap ones， while dominant species of woody plant and herb were not obvious in forest gaps， which were in the stage of competition and coexistence among populations. The plant diversity of herb is higher than that of woody in Larix kaempferi plantation， which showed the influence on plant diversity by forest gap is mainly caused by influencing the herbs. In practice of forest management， it′s necessary to pay attention to that herbs was important for developing plant diversity in early stage of forest gap formation. Clustershape selective cutting，followed by broadleaved tree repair planting could improve the plant diversity of Larix kaempferi plantation by simulating gap interfence in western Hubei.