To evaluate the antioxidant and lipid-lowering effects of the alcohol extract of Grifola frondosa (G. frondosa), the total sugar, protein, polyphenol, and triterpene contents of the alcohol extract were determined, and the antioxidant capacity was subsequently analyzed in in vitro antioxidant assays and Caenorhabditis elegans (C. elegans) models. In addition, lipid deposition in C. elegans was observed by Oil Red O staining, and the TG concentration and LPS activity were measured to explore the lipid-lowering potential of the alcohol extract. The results show that the alcohol extract of G. frondosa mainly consists of proteins, with a total protein content of 233.67 mg/g. The alcohol extract demonstrates significant DPPH, ABTS, and hydroxyl radical scavenging activities, and the corresponding IC50 values are 3.25, 0.38, and 1.73 mg/mL, respectively. Compared with those of the blank group, the CAT, T-SOD, GSH-Px, and LPS activities in the high-dose treatment group significantly increase by 4.33-, 4.88-, 2.28-, and 3.93-fold, respectively. Furthermore, lipid deposition, as well as the MDA and TG levels, decreases significantly. More specifically, the levels of MDA and TG in the high-dose group reduce by 55.62% and 50.66%, respectively. In conclusion, the alcohol extract of G. frondosa exhibits in vitro antioxidant capacity and can enhance the antioxidant enzyme activity in C. elegans. It also reduces lipid deposition and the TG concentration in C. elegans, indicating that it has a good lipid-lowering effect. This study provides a theoretical basis for the high-value utilization of G. frondosa.