This study employs first-principles calculations to investigate the impact of heteroatomic doping on the thermal transport properties of nanomaterials. We analyze two material systems: a two-dimensional (2D) h-BC₂N doped with C atoms (stoichiometric ratio B:C:N = 1:2:1) and a three-dimensional (3D) ZnSe doped with Cu atoms (stoichiometric ratio Zn:Cu:Se = 1:3:4). The results reveal that doping significantly reduces the thermal conductivity of both materials. Specifically, the thermal conductivity of 2D h-BC₂N decreases by 30%-50%, while that of 3D ZnSe drops by up to 80%.Phonon analysis demonstrates that the smaller reduction in h-BC₂N's thermal conductivity arises from the dominant contribution of optical phonons to heat transport, which accounts for 40% of the total thermal conductivity at room temperature. This phenomenon is attributed to intense four-phonon scattering in the structure, which suppresses the contribution of acoustic phonons and enhances that of optical phonons, limiting further significant attenuation of thermal transport via doping. Conversely, the drastic decline in ZnSe's thermal conductivity upon Cu doping stems from doping-induced suppression of structural harmonicity and promotion of anharmonicity, leading to pronounced reductions in phonon group velocities and lifetimes.This research provides comprehensive data and theoretical insights into doping effects on nanomaterial thermal properties, offering critical guidance for the application of doping nanotechnology in nanoelectronics and thermal management.