Natural reserves are the cornerstone of biodiversity conservation and play a crucial role in global forest ecosystem protection. Although many studies have evaluated the impact of natural reserves on land cover, human disturbances, and human welfare, the clarity of their effectiveness in reducing forest fragmentation remains unclear. Using natural reserves in China as an example, we analyzed the spatiotemporal characteristics of forest cover and fragmentation within the reserves from 2000 to 2022. We further employed propensity score matching to evaluate the effectiveness of reserves in mitigating the decline in forest cover and curbing forest fragmentation, and analyzed the spatial patterns of these effects. The study revealed that over half of the reserves experienced an increase in forest cover and a decrease in fragmentation, indicating an overall improvement in forest landscapes. Significant differences were observed in the forest landscape change patterns in the reserves across different provinces. The majority of provinces where forest cover had increased and fragmentation had decreased were located in the western and northeastern regions of China. In contrast, reserves in the southeastern provinces predominantly exhibited patterns of decreasing forest cover, coupled with either increasing or decreasing fragmentation. In terms of the effectiveness of forest landscape protection within the reserves, approximately 60.6% of reserves achieved positive results in mitigating the decline in forest cover, and the majority (64.4%) contributed positively to curbing forest fragmentation. Notably, there were significant differences in the average effects of reserves on mitigating forest cover loss and curbing fragmentation across provinces. The effectiveness of reserves in mitigating the decline in forest cover and curbing forest fragmentation was more significant in the southeastern region facing high anthropogenic pressure. Conversely, in the northwestern provinces with lower human pressure, the effectiveness was relatively weaker. However, the correlation between mitigating the decline in forest cover and curbing forest fragmentation was not significant (r=0.04, P>0.05). Overall, natural reserves in China have been effective in protecting forest landscapes, with 41.2% of reserves showing positive effects in both reducing forest cover loss and curbing forest fragmentation, while 84.0% demonstrated positive effects in at least one of these two aspects. These findings suggest that evaluating the effectiveness of natural reserves in reducing the decline in forest cover and curbing forest fragmentation simultaneously can provide a more comprehensive understanding of their impact on forest landscape protection. This study provides scientific support for the performance management of reserves and serve as a reference for the future development of China's natural reserve system.