Objective: To observe the dynamic change of anti-Müllerian hormone (AMH) in 1 year after chemotherapy which is the best biochemical marker of ovarian reserve in reproductive medicine setting and to evaluate the effect of gonadotropin-releasing hormone agonist (GnRHa)goserelin to prevent ovarian reserve function during (neo)adjuvant chemotherapy for young breast cancer patients.Methods: Between December 2015 and June 2017, 101 breast cancer patients of age ≤ 45 years with stagesⅠtoⅢ had been enrolled. The patients were assigned without interference to receive either (neo)adjuvant chemotherapy with goserelin (goserelin group) or without goserelin (chemotherapy group) as their own selection. AMH and menstrual status were evaluated before, during and 0.5 year, 1 year after chemotherapy. Primary end point was the incidence of low AMH value (<0.4 μg/L) at the end of 1 year. Secondary end point was the incidence of amenorrhea(the absence of menses in the preceding 12 months after assignment). Results: In the study, 51 patients chose to join the chemotherapy group, while the other 50 patients selected goserelin to preserve their ovarian reserve function. More unmarried or childless, hormone receptors negative,receiving breast conservation therapy patients with earlier stage selected goserelin before chemotherapy. The incidence of low AMH value was significantly higher in chemotherapy group than in goserelin group (74.5% vs. 38.0%, P<0.001) in 1 year after chemotherapy. The incidence of amenorrhea was consistent with AMH (56.9% vs. 24.0%, P=0.001). And more patients’ menstruation (78.9% vs. 54.5%) and AMH value (71.0% vs. 53.8%) recovered in goserelin group within 6 months after chemotherapy. In sub-group analysis, AMH and menstruation seemingly recovered more in goserelin group independent of age, chemotherapy regimen and use of tamoxifen. Especially, AMH value of 36.4% (8/22) patients in chemotherapy group and 18.4% (7/38) patients in goserelin group still maintained low level (<0.4 μg /L) although their menstruation had recovered 1 year after chemotherapy. In addition, 41 patients (20 patients in chemotherapy group, 21 patients in goserelin group) could be evaluated for the dynamic change of AMH and menstrual status during chemotherapy. The mean level of AMH in chemotherapy group declined rapidly to very low level before the 3rd cycle, while 70% of the patients kept presence of menstruation. At the same time, the mean level of AMH in goserelin group was still above 0.4 μg /L, but all of the patients had menopause.Conclusion: Our study has offered evidence that Goserelin with chemotherapy could protect against ovarian reserve failure for young breast cancer patients, now that more patients’ AMH value recovered earlier who had selected co-treatment. AMH may be a more precise marker than menstrual status to clinically evaluate ovarian reserve function pre-, during and post- chemotherapy.