The investigators are undertaking a parallel group, multicentre, randomised controlled trial of 30 primary ITP adult patients from 3 medical centers in China. They will be randomly assigned in a 1:1:1 ratio into three groups .The patients in group A (total 10 patients) will receive rhTPO at a dose of 300Units/kg ,daily for 14 consecutive days;The patients in group B will receive rhTPO at a dose of 300Units/kg ,one times every other day for 7 times.The patients in group C will receive rhTPO at a dose of 300Units/kg ,daily for 7 consecutive days .All the patients will follow with a flexible dosage depending on platelet count during the following 12 weeks.