Abstract: In order to explore the method for removing mordant from natural dyes printed fabric white ground, the suitability of removing Fe3+ mordant agent with oxalic acid as removing agent was investigated. The influence of oxalic acid on synthesis Long gum as thickener was evaluated by measuring the rheological properties. The effect of different factors, i.e. steaming temperature, humidity, time and concentration of oxalic acid, has been studied by testing the whiteness and the strength properties of silk fabric. The results showed that oxalic acid had no effect on the rheological properties of synthesis Long gum paste. The best results were obtained by using oxalic acid at a concentration of 0.35 to 0.40 percent of the weight of printing paste, and steaming temperature 100 ℃, humidity 100%, steaming time 8 min.