Abstract: In order to elucidate of the role of corn fiber in preventing constipation and alleviating constipation symptoms,the constipation model of mice was used to investigate the effect and dose of two common corn fiber(oat dietary fiber and wheat dietary fiber)on laxative function. 192 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 divided into blank control group,model control group oat dietary fiber groups(low,middle and high)and wheat dietary fiber groups(low,middle and high). Low,medium and high dose concentrations were 0.5,1.0 and 2.0 g/kg,respectively. After 14 d of intervention,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 ink propulsion rate of oat fiber and wheat fiber low,medium and high dose groups increased gradually,among which the medium and high dose group reached the significance(P<0.05). At the same dose,there was no difference in the effect of two common corn fibers on the intestinal ink propulsion rate. Compared with the model control group,the fecal number and fecal weight of the oat fiber medium dose group and the wheat fiber high dose group were significantly increased within 6 h(P<0.05),but there was no difference between the two groups(P>0.05). Therefore,the two kinds of grain dietary fiber both have the laxative function,but the dose is different. The effective dose of oat fiber(1.0 g/kg)is lower than that of wheat fiber(2.0 g/kg).