Apple flesh pomace was used as raw material,extraction and optimization of soluble dietary fiber by X-cell cellulose enzymatic methods were studied.The physicochemical properties including water holding capacity,expansion force,apparent viscosity and ultra-structure were analyzed.The optimum conditions was that the enzyme dosage of 75 U/g,hydrolysis temperature of 50 ℃,pH 4.6,reaction time 5 h.Under the above conditions,the soluble dietary fiber extraction rate was up to 18.90%.The water holding capacity and the expansion force of the residue was higher;the solubility of fiber was higher,the concentration of the apparent viscosity was lower.In the IR spectrum,there was a relatively stronger sugar absorption peak,and microstructure changes of the fiber were observed under the electron microscope.