The randomized, placebo-controlled multicenter trial is conducted in five centers in China. After screening and obtaining the signed informed consent , the participants are randomly divided into three groups: acupuncture group (Acu.+IVF），sham acupuncture group（Sham Acu. +IVF），and the control group (only IVF).

Inclusion Criteria:

1. Married women aged 25-40;
2. Repeated implantation failure for unknown reasons (experienced 2 or more embryo transfers of good-quality embryos without achieving clinical pregnancy);
3. Transplantable Day 3 high-quality frozen embryos or frozen blastocysts (≥3BB);
4. Estrogen and progesterone replacement therapy (HRT), endometrial thickness ≥7mm on the day of endometrial transformation.

Exclusion Criteria:

Patients who met any of the following conditions were not included.

1. Those who prepare for PGD;
2. Recipients of egg donors;
3. Chromosomal abnormalities in both or one of the couples (excluding chromosome polymorphism);
4. patients with implantation failure due to known embryonic factors;
5. Uterine lesions that may affect implantation (including uterine malformation, >4cm intramural fibroids，submucosal fibroids, adenomyosis, uterine tuberculosis, intrauterine adhesions, etc.
6. Repeated spontaneous abortion (2 or more fetal loss before 28 weeks of gestation);
7. Patients with other endocrine diseases, such as thyroid disease, hyperprolactinemia, insulin resistance, diabetes, adrenal disease, etc., and poor control of hormone levels in the last 3 months;
8. Clearly diagnosed autoimmune diseases such as systemic lupus erythematosus, rheumatoid arthritis, antiphospholipid syndrome, etc.;
9. Hydrosalpinx untreated;
10. BMI less than 18 or higher than 25kg/m2;
11. People with previous history of needle sickness;
12. Those who have previously participated in this study or received acupuncture treatment in the past 3 months.
13. Any situation that researchers consider inappropriate for participating in this study.

To maintain blinding in patients, outcome assessors, and statisticians, the allocation sequence was concealed until the end of the study.