A small-molecule self-assembled nanomaterial (SMSN)-enriched extract from Eucommia ulmoides Oliv. leaves (EuNE) was isolated and purified as an alternative to high-purity SMSNs, with the aim of reducing production costs and facilitating industrial application. A self-assembly performance-guided fractionation strategy was applied to screen and identify functional EuNE components, which were further characterized using chromatographic techniques. The encapsulation efficiency and stability of curcumin loaded into EuNE self-assembled nanoparticles (EuNE NPs) were systematically evaluated. The EuNE fraction obtained via methanol extraction, petroleum ether fractionation, and ethanol precipitation exhibited excellent self-assembly capability. The resulting EuNE NPs showed an average particle size of 232.79 nm and a surface charge of -30.13 mV. Oleanolic acid (38.56 mg.g-1) and ursolic acid (68.35 mg.g-1) were identified as the major carrier components, forming nanoparticles through synergistic hydrogenbonding and electrostatic interactions. Curcumin encapsulation efficiency in EuNE NPs reached 77.40%, accompanied by markedly improved stability under ultraviolet irradiation, elevated temperatures, different pH conditions, and varying ionic strengths. In simulated gastric fluid, 69.34% of curcumin was released within 3 h, while cumulative release in simulated intestinal fluid reached 44.60% over the same period, demonstrating sustained-release behavior. These results indicate that SMSN self-assembly can be achieved without high-purity monomeric components and highlight the potential of Eucommia leaf extracts for the development of cost-effective, high-performance natural nanocarrier systems.