Enzalutamide (Enza) and abiraterone (Abi) were approved for the treatment of metastatic castration resistant prostate cancer(mCRPC) patients. Resistance to Enza and Abi occurs frequently and renders mCRPC patients incurable. Therefore, there is great unmet medical need to identify resistant mechanisms to improve the treatment outcome of mCRPC. We have shown that overexpression of AKR1C3 is responsible for the elevated intracrine androgen biosynthesis in prostate cancer cells. Up-regulation ofAKR1C3 is correlated with anti-androgen resistance. We therefore sought to knock down AKR1C3 with specific siRNA/shRNA and small molecule drug to confirm its role in androgen synthesis and drug resistance. In this report, we used siRNA, shRNA specific toAKR1C3 and a small molecule inhibitor Indomethacin to target AKR1C3. At cellular level, we demonstrated that knockdown AKR1C3may 1. Restore sensitivity to anti-androgen drugs such as enzalutamide and abiraterone. 2. Reduce AR-V7 level. 3. Inhibit AR transactivation activity. 4. Abate intratumoral androgen synthesis. Using Indocin to target AKR1C3 in vivo is efficient in reducing tumor sizes and further successful in blocking tumor growth when combined with either enzalutamide or abiraterone. Our results confirmed that blocking AKR1C3 restores drug sensitivity of CRPC or drug resistant cells to anti-androgen treatments. TargetingAKR1C3 with Indomethacin in combination with enzalutamide shows great potential in advanced prostate cancer treatment.