Qinghai Province is a critical ecological security barrier on the Qinghai-Tibet Plateau. Understanding the spatiotemporal dynamics of its ecological environment quality is essential for promoting ecological civilization and advancing the province’s "ecology-first" development strategy. To address the significant salinization issues in parts of the region, this study incorporates a salinity indicator into the Remote Sensing Ecological Index (RSEI) and applies full-sequence normalization to develop a modified Remote Sensing Ecological Index (mRSEI). From the perspective of ecological functional zoning, geographic detectors and trend analysis are employed to systematically assess the spatiotemporal variations and driving forces of mRSEI from 2000 to 2024. Results reveal that: (1) Qinghai’s mRSEI exhibits a gradual upward trend over the study period, with improvements in all ecological zones except the Northern Tibetan Plateau alpine desert grassland; (2) The province"s ecological quality remains at a moderate level overall, with the highest quality in the Qilian Mountains forest and alpine grassland zone, and the lowest in the Qaidam Basin desert zone; (3) The driving factors of mRSEI exhibit significant regional differences. For example, in the Qilian Mountains Forest and Alpine Grassland Ecological Zone, the primary drivers are net primary productivity, soil moisture, and annual precipitation, whereas in the Northern Tibetan Plateau Alpine Desert Grassland Ecological Zone, soil moisture is the dominant influencing factor. These findings provide a scientific basis for the refined management of ecological zones and the development of targeted conservation policies in Qinghai Province.