Abstract: The inner-S-doped polystyrene capsules with diameter of 200-800 μm were fabricated using the density-match microencapsulation method and the polystyrene sulfurnate (PSS) was used as doped raw material. The drying progress of PS capsule was studied by non-contact X-radiography and the appearance of S element in inner surface was characterized by X-ray photoelectron spectrum (XPS). The inner-S-doped uniformity can be affected by gravity and interfacial tension. The PSS concentration plays a key pole in the inner-S-doped uniformity and the capsules with inner-S-doped uniformity can be obtained when the PSS concentration is 0.2%. There are 8.57×10⁶ sulfur atoms on every 1 μm² inner-S-doped surface of the capsules with diameter of 300 μm.