Datong County in Qinghai Province is located in the transition zone between the Qinghai-Tibet Plateau and the Loess Plateau, this area is known as the "Water Tower of Xining" , holding a significant ecological status. Maintaining the good health status of the secondary forest of the main pioneer tree species Betula platyphylla in this area is conducive to giving full play to its water conservation function and is of great significance for maintaining regional water resource security. Given the complexity and multi-factorial nature of the degradation phenomena in this region. The purpose of this study was to evaluate the health status of Betula platyphylla secondary forests with varying densities in Datong County, Qinghai Province, and to reveal the main influencing factors, thereby provide a scientific basis for the restoration and reconstruction of degraded natural forests. To this end, the four latent variables - productivity, soil quality, stand structure, and system stability – as well as 18 observable variables were selected as forest health assessment indicators, and the weights of the assessment indicators were calculated using validated factor analysis (CFA), based on which the composite scores of the health of stands with different densities were calculated. The results showed that the standardized path coefficients of the four latent variables on forest health were 0.74, 0.90, 0.09, and 0.70, respectively, and all reached the significant level. The weight analysis showed that soil quality had the highest combined weight (0.3704), followed by productivity (0.3045) and system stability (0.2880), while stand structure had a relatively low weight (0.0371). The study shows that soil quality directly affects the water and nutrient absorption capacity of the stand, and it is the foundation for maintaining stand stability and productivity. By analyzing the forest health composite scores of stands with different densities, it was found that the composite scores of sample plots with densities in the range of 300—500 plant/hm2 were the highest, which were significantly better than those of other density intervals; too high density (more than 800 plants/hm2) resulted in lower health scores, mainly due to intensified resource competition, which restricted tree growth and contributed to an increase in forest pests and diseases. Overall, maintaining a moderate and reasonable stand density (300—500 plants/hm2) in the secondary forest of Betula platyphylla can effectively maintain its soil quality and productivity, and thus maintain a better level of stand health. This provides an important reference for future forest management and ecological restoration work, especially in terms of forest restoration and density control.