In this study, we aimed at producing a MFNP consist of a dielectric core encapsulated fluorescein coating by a thin gold shell, which facilitate it with highly favorable optical and chemical properties for biomedical imaging and therapeutic applications. We have composed a novel multi-functional nanodesign, Sample A3, with fluorescein encapsulated in SiO2 nanoparticles with gold shell. The A3 nanoparticles were uniform in size, no aggregation, homogeneous and stable in the solution under the SEM image system. We have also investigated its cytotoxicity to A10 human smooth muscle cell line by MTT assay, and found that the novel sample A3 were of little cytotoxic to the cells. In conclusion, we have proposed a novel method of preparing multi-functional nanoparticles assemblies, which has added fluorescein to SiO2 in a gold shell, to make it simultaneously have the functions of photothermal therapy and tracer.