Abstract: The sex ratio of green turtles (Chelonia mydas) is determined by incubation temperature, so global climate change may affect the future survival of their populations. To evaluate the effects of global climate change on the future green turtle nesting population at the Xisha Islands and to provide a scientific basis for conservation strategies, without disturbing the natural incubation process, this study monitored sand temperature near the green turtle nests from December 2019 to December 2020 at Qilianyu (Xisha Islands). Temperature data loggers were used to record sand pit temperatures, and the data were combined with nesting time, metabolic heat during incubation, and the correlation between air temperature and sand pit temperature to estimate the feminization ratio of nests in 2020. The results showed that the year-round sand temperature of Qilianyu ranged from 22.3 to 34.1 ℃, with the highest in July and the lowest in February. The daily temperature variation and its amplitude were relatively small throughout the year. There was a significant and positive correlation between the sand temperature and the air temperature (P＜0.05). The rainfall at Qilianyu was mainly concentrated from August to November in 2020, and a significant positive correlation was observed between monthly temperature variation and rainfall (P = 0.001). The sand temperature fluctuation in the vegetation boundary at North Island, the core nesting island, was lower than that in the exposed beach exhibiting a pattern of warmer winter and cooler summer. In 2020, 149 nests were recorded at Qilianyu, with nesting occurring almost year-round except in January and February, peaking from May to September. It was estimated that 119 nests were fully female-biased, mainly laid in May to August, accounting for 79.9% to 92.6% of the total nests. Under the trend of global warming, the future hatchlings at Xisha Islands, the largest green turtle nesting ground in China, are predicted to be predominantly female, which warrants significant attention regarding the impact on the green turtle population in China.