Objective To explore the value of ultrasound B in observing follicle growth and developement ovulation and treatment of sterility.Methods Use ultrasound B to observe ova developement of 70 patient's 72 natural period and 50 drug ovulation period.Results The average daily growth of natural period follicle is 1.90mm,the follicle average diameter before ovulation is 21.30mm. The average growth of drug-promoted ovulation follicle is 2 42mm,the average diameter of follicle before ovulation is 23 85mm. The follicle grow at different speed before ovulation.Conclusion Through the serial observation of follicle's growth、 developement、ovulation by ultrasund B,we can find out the reasons of sterility,guide clinical treatment, increase the pregnancy rate of the patients.