Arcgis converts wgs 1984 into xian 1980.

Projcs [" Xian _ 1980 _ 3 _ degree _ GK _ zone _ 37], GEOGCS["GCS_Xian_ 1980 ",DATUM["D_Xian_ 1980". 6378140.0,298.257], prime number ["Greenwich ",0.0), unit ["Degree", 0.00.

Wgs is geodetic coordinates,

You didn't define projection at all. Open arctoolbox. There is a definition projection in the projection and transformation of data management tools. Choose Xi 'an 80 in Goscliffe. If not, please open it. Source files in prj files, and copy the above paragraphs. If the calculation is correct, Shanxi should be at 37 degrees ~ ~