Protein fibers are attractive topics in the past decades. Among them, silk and wool fibers are very popular due to their luster, smooth surface and comfort. In order to reach union dyeing of silk/wool blends, chlorination pretreatment or introduction of low-temperature dyeing auxiliary for wool are selected and compared. The results showed that chlorination pretreated wool/silk dyed with weak acid dyes, can reach union dyeing under 80 oC, possibly under 70 oC. On the other hand, introduction of low-temperature dyeing auxiliary can slightly improve the union dyeing at different temperature ranges according to selection of weak acid dyes.