Abstract: This study was to evaluate the preventive effect of low molecular weight partially hydrolyzed guar gum(L-PHGG)on diphenoxylate-induced constipation in Kunming mice. The effects on the small intestinal propulsion rates,the defecation time of the first black stool,the wet weight and number of defecation within 6 hours after administration,serum parameters,HE staining of small intestine,and the contents of organic acids in feces were investigated. The results showed that compared with the constipation model mice,the mice those were fed L-PHGG at low,middle or high-dose presented in higher gastrointestinal transit,increased by 32.4%,54.4% and 81.6% respectively;and the positive control(bisacodyl group)increased by 57.0%. The wet weights of defecation within 6 hours after low,middle or high-dose of L-PHGG increased by 64.3%,79.1% and 85.6% respectively,while the bisacodyl group increased by 78.6%. In addition,the levels of substance P(SP)of the L-PHGG at low,middle or high-dose increased by 27.8%,44.1% and 70.1% respectively,and the bisacodyl group increased by 53.0%. Serum vasoactive intestinal peptide(VIP)of the L-PHGG at low,middle or high-dose increased by 11.1%,9.3% and 32.6% respectively,and the bisacodyl group increased by 10.6%. HE staining of small intestinal showed that all L-PHGG groups presented less rupture,weaker damage,longer length and higher number of intestinal villi. The total content of lactic acid,acetic acid and propionic acid of low,middle or high-dose of L-PHGG increased by 27.7%,35.3% and 50.5% respectively,but the bisacodyl group only increased by 25.3%. In conclusion,these results suggested that L-PHGG of low,middle and high-dose had preventive effect on constipation in mice,especially for the middle and high-dose groups,which provides scientific supports for the development of L-PHGG as functional food for gastrointestinal tract.