The purpose of this is article is to design the thermal sensors using Plasmon effects in the waveguide with composite crust. Therefore, the effects of temperature in optical constants of metal nano-particles were first investigated and used the Mid-range theory model to investigate the thermal features of composite. It is also shown how the waveguides with composite crust and the pure dielectric core can be utilized as the thermal sensor. Also, by the constant density of the metal nano-particles in the crust, the increase in the temperature leads to the changes in the Plasmon and collision frequencies and dispersion. The simulation results of the waveguide with composite crust reveal that the composite waveguide with higher density leads to better imprisonment of mode and shows the thermal effects extraordinarily.