During succession of plant communities, the processes are continually influenced by a variety of disturbances, which may be caused by natural disasters or anthropogenic activities. Although the characteristics of disturbances are different, they can all result in the changes in species composition and diversity, structures and functions of plant communities. Recently, effects of disturbances on ecosystems have become more and more complex for the gradually frequent and strong activities of human beings. It is therefore, important to understand the occurrence processes of disturbances and to forecast the results of different disturbances, which are in favour of the conservation of natural ecosystems and other human practices. In this paper, concepts and characters of disturbances were introduced. Some hypotheses of effects of disturbances on biodiversity were enumerated. Of which, the intermediate disturbance hypothesis was the most popular one, which had become the basics of many researches in this field. Then, the effects of disturbances on plant species composition were discussed. The influences of disturbances on plant species diversity were also analyzed in the aspects of the type, the intensity and the frequency of disturbances. It could be found that the effects of disturbances on plant species composition and diversity were related to the characteristics of disturbances and plant communities, bionomic of plant species, and the resources of the disturbed locations. In addition, we analyzed the effects of canopy gap, which is one kind of the important small-scale disturbances in forest ecosystems, on the maintaining of diversity and succession of forest ecosystems. Finally, some problems in this research field were summarized and propositions were made to offer the references for further studies.