The wide band-gap semiconductor, ZnO, has been proposed as one of the good host for Er3+ ions. In this investigation S was doped into the Er-containing ZnO specimens through the heat treatment in a H2S gas atmosphere. After sulfurization, the photoluminescence (PL) peak centered at 675nm from the ZnO host became much weaker, and accordingly the absorption peaks of Er3+ at 526nm, 550nm, and 665 nm became weaker. Also, the PL intensity around 1.54µm decreased after the sulfurization. However, when the sulfurized specimens were annealed at 1000oC in air, the PL intensity increased by about 3 times. The effects could be due to the modification of the local structure around the Er3+ ions in ZnO.