Abstract: Citrus residues was treated with citric acid to extract soluble dietary fiber (SDF) and the yield of soluble dietary fiber was used to be an indicator. On the basis of single-factor experiments, response surface analysis based on Box-Behnken experimental design were carried out to optimize the extraction process of soluble dietary fiber. As indicated by variance analysis and interaction analysis, the optimal extraction parameters were found as follows:mass fraction of citric acid 3.38%;material-to-liquid 1∶24;oscillation time 69min;temperature72℃. Under the optimized conditions, the actual yield of soluble dietary fiber was 21.10% ±0.16%. It could be well fitted with model and was reliable and applicable for actual prediction.