Abstract: This study designed and synthesized a new drug-loading nanomaterial, the three-armed star-shaped polymer compound (TaSPC), and loaded the broad-spectrum fungicide fluazinam to prepare TaSPC/fluazinam nanocarrier particles. The principle and drug-loading performance of TaSPC loading fluazinam were investigated by molecular docking simulation and ultraviolet spectrophotometry. The appearance and particle size changes before and after loading fluazinam onto TaSPC were compared and analyzed by transmission electron microscopy and scanning electron microscopy. The physicochemical properties of TaSPC and TaSPC/fluazinam were characterized by Zeta potential analysis, contact angle measurement with strawberry leaves, and uptake test with Rhodamine 6G. The in vitro and in vivo inhibitory effects of TaSPC/fluazinam on four plant pathogenic fungi, the toxicity of TaSPC to human umbilical vein endothelial cells, and the toxicity of TaSPC and TaSPC/fluazinam to Apis mellifera ligustica Spin. were determined. The results indicated that TaSPC could spontaneously combine with fluazinam through hydrophobic interaction, with a pesticide loading rate (PLC) of 9%. The particle size of TaSPC/fluazinam was 17.86 nm, which was significantly reduced by 71.4% compared to the original fluazinam (62.46 nm). After loading with TaSPC, the contact angle of the TaSPC/fluazinam droplet on strawberry leaves decreased from 44.08° to 33.60°, a significant reduction of 23.78%. The inhibitory effect of TaSPC/fluazinam on plant pathogenic fungi was significantly enhanced compared to the original fluazinam. Among them, the inhibitory activity against Botrytis cinerea was the highest, with an inhibition rate of 75% at a dose of 0.2 mg/L, an increase of nearly 60% compared to the original fluazinam. Within a reasonable application range, TaSPC had low cytotoxicity, and both TaSPC and TaSPC/fluazinam had low toxicity to pollinating bees. The study demonstrated that TaSPC is a significant benchmark for the development of efficient and low-toxicity nanocarrier materials and the reduction of pesticide use.