Background: Gold nanoparticles have anti-aging effects through their mechanism for the final product of the glycation process, which is widely used in cosmetic preparations. Some plant extracts can be used as bioreductors in the synthesis of gold nanoparticles, one of the extracts from kacip fatimah (Labisia pumila) because of its high antioxidant properties. Objective: In this study, we develop formulation cosmetic serum that contains of green synthesized gold nanoparticles reduced by kacip fatimah (Labisia pumila) and to evaluate its characterize and stability. Material and Methods: Serum formulations were carried out with variations in the concentration of hydroxyethyl cellulose as gelling agents and gold nanoparticles made by HAuCl₄ that reducted with L. pumila extract as the active ingredient. Gold nanoparticles were characterized using UV-Vis spectrophotometers and Particle Size Analyzer (PSA) Zetasizer. Results: Formed nanogold average size of the nanoparticles were 69.34 nms with a potential zeta -26.1 mVs and polydispersity index 0,463. The one selected of gelling agent concentration is 0,5%. Cosmetic serum containing various of nanogold 0.2%, 0.4%, 0.6%, and 0.8%. Characterization and evaluation was carried out on cosmetic serum, which gave the results of viscosity according to the range 300 - 400 cPses; pH is in the range 5-6.5, scattered power diameter depends on the range 7-10 cm, and provide flow properties containing the pseudoplastic flow. Conclusion: Cosmetic serum contain gold nanoparticles can be prepared and the physical stability test using a cycling test gave a good and stable cosmetic serum because it did not have a significant difference based on physical appearance, homogeneity, viscosity and pH measurement.