Platelet-rich plasma nowadays has been widely applied in different clinical scenarios, such as orthopedics, ophthalmology and wound healing to improve the tissue regeneration. However, little is known regarding the application of PRP in the treatment of thin endometrium. This study aimed to evaluate the Platelet-rich plasma (PRP) as an adjuvant therapy before embryo transfer in infertile women representing with refractory thin endometrium (<7 mm) during the frozen embryo transfer cycle. The present study was a randomized clinical trial prospective interventional study was conducted, involved 50 cases. Intrauterine autologous Platelet-rich plasma (PRP) administration was performed at the estrogen-primed FET cycle . The EMT of 31 patients (62%) out of 50 still <7 mm after 1st inject and need other PRP inject. The EMT of 21 patients out of 31 still <7 mm after 2nd inject and need other PRP inject. The EMT of 15 patients out of 21 still <7 mm after 3rd inject and need other PRP inject. The EMT of 35 patients out of 50 (70%) reach more than 7 mm after PRP inject which is statistically highly significant increase in EMT after each PRP injection. Intra uterine PRP is effective in increasing endometrial thickness in reapted implantation failure in FET cycles due to refractory thin endometrium. Intra uterine PRP is easy, safe (being an autologous resource) and with very low-cost method.