The thermodynamic, dynamical and structural properties of gold nanoparticles (AuNPs) of sizes 603-28897 atoms are studied by using molecular dynamics (MD) simulations based on the Embedded-Atom-Method (EAM) potential. The radial distribution function (RDF) and common neighbors analysis method (CNA) are used to characterize the local structure of the AuNP during the heating processes. The behavior of the Lindemann index of each region for the AuNP with respect to temperature is studied to comprehend the melting mechanism. The simulation results revealed that that the melting starts from the free-surface and proceeds towards the core for AuNP. Moreover, it is found that the complete melting temperature of AuNP at different heating rates decreases drastically with decreasing particle size. The global behavior of the size-dependent melting point evaluated in the present study is in good agreement with the previous experimental data. Furthermore, dynamical properties of AuNP in liquid state are carried out by using the velocity autocorrelation function (VAF) through which the temperature dependence of the self-diffusion coefficient of the AuNP is computed. Besides, it is found that the activation energy found through the Arrhenius equation is less than the experimental value for the Au bulk in the liquid state.