1. The tolerance test of randomized，double-blind, placebo-controlled multiple-dose oral administrations.2 dosage groups are set up.Each group contains 8 subjects,evenly composed of men and women.The beginning dosage of the study is 160mg/L.Subjects who have successfully completed tests of the beginning dosage group and passed the safety assessment will enter the test of next dosage group(320mg/L) according to the same method.