  S-stars in the Galactic Center are excellent testbeds of various general
relativistic effects. While previous works focus on modeling their orbital
motion around Sgr A*--the supermassive black hole in the Galactic Center--here
we explore the possibility of using the rotation of S-stars to test the de
Sitter precession predicted by general relativity. We show that by reorienting
the rotation axes of S-stars, de Sitter precession will change the apparent
width of the absorption lines in the stellar spectra. Our numerical simulations
suggest that the newly discovered S4714 and S62 are best suited for such a test
because of their small pericenter distances relative to Sgr A*. Depending on
the initial inclination of the star, the line width would vary by as much as
$20-76\,{\rm km\,s^{-1}}$ within a period of $20-40$ years. Such a variation is
comparable to the current detection limit. Since the precession rate is
sensitive to the orbital eccentricity and stellar quadrupole structure,
monitoring the rotation of S-stars could also help us better constrain the
orbital elements of the S-stars and their internal structures.
