Close-to-nature forest management is a kind of forest management model which imitates and approaches the nature. Making full use of the natural growth and development principles of forest ecosystems, it employs planning and designing of forest management activities based on forest natural regeneration to optimize the structure and function of the forests. In addition, by combining economic needs with ecological benefits, it promotes the nearest natural state of the forest. The main tree species of a plantation in Saihanba Nature Reserve are Prince Rupprecht's larch (Larix principis-rupprechtii Mayr) and Mongolian Scots pine (Pinus sylvestris var. mongolica). The close-to-nature forest management measures were implemented in this plantation by strictly controlling the outside interference from humans and by timely tending and improving the forest growing environment. In order to study effects of different stand types of Prince Rupprecht's larch on the diversity of insect community in the plantation under close-to-nature forest management, the structure of the insect community was studied in six stand types of the Prince Rupprecht's larch pure and mixed forests in Saihanba Nature Reserve. The insects were collected by the sweep net method, and the diversity index, similarity, principal component, and stability of insect communities in different forest types were analyzed. In total, 9542 insects, belonging to 7 orders, 68 families, 187 species, were collected; Diptera, Hemiptera, and Coleoptera were the dominant groups. The results indicate that there were differences in species and individual number of insects in the six stand types, and similarity analysis revealed different insect community structure. The community diversity analysis showed that the richness index and Shannon-Wiener diversity index in pure and mixed forests were both high. Principal component analysis showed that predatory and parasitic groups in each stand type were the main factors influencing the community structure; they had a stronger effect on the forest compared to the phytophagous group. Stability analysis showed that the structure of insect community in different forest stand types had high stability. Under the close-to-natural forest management in Saihanba Nature Reserve, the plantation not only showed a high biological diversity, but the forest ecosystems were more stable and showed higher effective resistance to external disturbances. Therefore, traditional forest management methods should be substituted with an approach where the relationships between different species in a forest ecosystem are maximally employed and the forests are managed by rational allocation of the spatial structure of trees and selection of appropriate tree species and planting density. The most important points include establishing a management philosophy of the close-to-natural forest management and managing the plantation appropriately. Only then can the forest ecosystem reach higher stability and play an important role in regulating the forest ecosystem itself. The ultimate goals are to achieve ecological as well as economic benefits of forest resources and to reach the sustainable use of the biodiversity and the state of healthy forest development.