Androgen deprivation therapy has been used as a standard clinical treatment for prostate cancer, but the disease generally progresses to castration-resistant prostate cancer in a very short time. Enzalutamide (ENZ) is an emerging second-generation androgen receptor (AR) antagonist used for the treatment of patients with nonmetastatic castration-resistant prostate cancer (CRPC). However, due to the rapid onset of drug resistance, it provides only a modest increase in survival. Here, we propose a convenient and effective androgen receptor antagonist drug delivery strategy, that is, the use of a biocompatible nanoparticle (NP) drug delivery system for drug delivery to improve its bioavailability and therapeutic performance. Although the particle size of the phenylpropyl polymer (8P4) nanoparticles is small, it has a high drug-carrying capacity. ENZ-8P4 NPs can increase drug delivery efficiency, enhance drug cytotoxicity, and reduce the half-inhibitory concentration (IC50) of the drug. In addition, in vivo experiments confirmed that ENZ-8P4 preferentially accumulates in the tumor and significantly inhibits tumor growth. Hence, the 8P4 drug delivery system loaded with enzalutamide has excellent potential for the treatment of prostate cancer.