Gold nanoparticles (AuNPs) have been the subject of intense research for use in biomedicine over the past couple of decades. AuNPs, also referred to as colloidal gold, possess some astounding optical and physical properties that have earned them a prime spot among the new promising tools for medical applications. Today, AuNPs are offered to provide the clinical laboratory with more sensitive, faster, and simpler assays, which are also cost-effective. AuNPs can be used to develop point-of-care tests and novel testing strategies such as in drug targeting, disease detection, molecular recognition, and biological labels. The typical structure of AuNPs is spherical nano-sized gold particles, but they can also be composed of a thin gold shell surrounding a dielectric core, such as silica (gold nanoshells). their size range from 0.8 to 250 nm and are characterized by high absorption coefficients. AuNPs have some unique optical properties, such as enhanced absorption and scattering, where the absorption cross-section of AuNPs is 4~5 orders of magnitude greater than that of rhodamine 6G. When AuNPs aggregate, interaction of locally adjacent AuNPs (plasmon-plasmon interaction) shifts their color to blue. Thus, the binding of AuNP-labeled entities to their respective target would lead to aggregation of the nanoparticles and a detectable shift in the optical signal. The strong absorption of AuNPs can also be used in colorimetric detection of analytes by measuring changes in the refractive index of the AuNP’s environment caused by adsorption of the target analytes. However, a large number of surface atoms of nanoparticles have huge surplus bonding ability, because of surface effect of gold nanoparticles, result in reuniting and sinking among the nanoparticles which make them unstable. In order to detect traces of carcinoembryonic antigen, one of the tumor targets, a new kind of gold nanoparticle with hyperchormic effect and fluorescence sensitization effect material needs to be prepared. In this paper, novel mercaptan derivative of nanogold particles are prepared and studied using transmission electron microscopy (TEM), ultraviolet-visible absorption spectra (UV-Vis), fluorescence emission (FE) spectrum and infrared spectrum (IR) methods. The UV-Vis and FE results show the presence of new ligands mercaptan, more electrons from the orbit of ligand which can excite to the central ion related orbits and increase fluorescence of gold. Fluorescence sensitization effect was observed when mercaptan derivatives of nanogold interacted with carcinoembryonic antigen (CEA) and no fluorescence sensitization effect was found when nanogold interacted with carcinoembryonic antigen (CEA). The study of CEA hyperchromic mechanism of mercaptan derivatives nanogold and the CEA by the method of infrared spectrum, shows that the randomized OH bonds in the Au-protein interaction, showed more on the outside of the plane of bending vibration after the interaction with the mercaptan derivative nanogold, making the energy transfer from mercaptan derivatives nanogold to protein easy; leading to its fluorescence sensitization effect.