Abstract: In order to study the effect and effective dose of polydextrose on the laxative function,120 Kunming male mice were randomly divided into two trail groups,one for small intestine movement experiment and the other for defecation experiment. Each trail group was randomly divided into blank control group,model control group and low,middle and high polydextrose groups. Low,medium and high dose concentrations were 0.5,1.0 and 3.0 g/kg,respectively. After 14 days of intervention,loperamide was used to establish the constipation model of mice,then the intestinal ink propulsion rate,first black stool time,fecal number and fecal weight within 6 h were measured.The results showed that,compared with the model control group,the intestinal propulsion rate of the low,middle and high dose polydextrose group had an increasing trend,but the difference was statistically significant only in the high dose group(P<0.05);there was no significant difference in the first defecation time and the number of fecal particles in the low,middle and high dose polydextrose groups(P>0.05). There was no difference in fecal weight between the low and meddle dose polydextrose groups and the model control group,but the fecal weight of the high dose polydextrose group was extremely significantly higher than that of the model control group(P<0.01).Therefore,high dose of polydextrose had a laxative effect,the effective dose was 3.0 g/kg.