Based on realistic measurements in China, shadowing characteristics at the frequency of 2350 MHz were investigated in typical High-Speed Railway environments. After confirming that the measured shadowing satisfies wide-sense stationarity (assessed via the reverse arrangement test method), we quantify the shadowing correlation. Three types of correlation models are compared for the shadowing characterization, and the Normalized Mean Square Error is used to determine the best matching model: a single decaying exponential function. Decorrelation distances were found to be 11.9 m, 17.7 m, and 8.3 m in our three HSR scenarios, respectively. The results should be useful for the evaluation and verification of wireless communication in High-Speed Railway scenarios.