Prepared gold nanoparticles and covered with gelatin were synthesized with little difference in gelatin concentration by reducing the volume of a chloric acid stock solution with a fixed volume of sodium citrate dihydrate (34 mm) solution. The nanoparticles had excellent colloidal stability, and TEM revealed the formation of well-spherical gold nanoparticles (AuNPs) of various sizes. The method produces particles with sizes ranging from 10 to 20 nm. The gelatin AuNPs exhibit size-dependent surface Plasmon resonance behavior as measured by UV visible spectroscopy, with SPR ranging from 518 to 543 nm depending on the concentration of gelatin used. The goal of this study is to assess dynamic therapy in vivo using a 532 nm wavelength laser with gelatin-coated gold nanoparticles as photosensitizers. According to the findings of the study, the green diode laser has the best photodynamic therapy effect on cancer cells in vivo after cells photosensitization with gold nanoparticles covered with gelatin at a concentration of 1% and an exposure time of 60 seconds.