Soluble dietary fiber (SDF) was prepared by Trichoderma viride fermentation by using apricot pulp as the raw material. A four-factor and three-level response surface methodology was applied to optimize the fermentation conditions affecting the extraction rate of SDF. The optimum fermentation conditions were listed: crude enzyme volume, 9.59 mL g(-1); fermentation temperature, 43 °C; initial pH, 5.36; fermentation time, 6.47 h. Under these conditions, 15.69% yield was obtained and its relative error with the predicted theoretical value (15.87%) was 1.14%. The dietary fiber content of SDF was 84.0% whereas it was found to be 43.1% in apricot pulp flour. The anti-diabetic effect of apricot pulp SDF on rat models of diabetes was investigated. Both the blood glucose level and body weight were significantly changed in apricot pulp SDF-treated groups compared with the diabetic group (p < 0.01) after intragastric administration for 28 days. In addition, SDF elicited inhibitory effects on the α-glucosidase activity with an IC50 of 17.458 mg mL(-1). These results implied that apricot pulp SDF relieved the symptoms of diabetic rats.