In this paper the theoretical calculation methods for CP(T) (molar heat capacity at constant pressure) values of nanoparticle and nanocrystalline are investigated. Theoretical formulas for calculating CP(T), Debye temperature and volume expansion coefficient of nanoparticle using melting point of nanoparticle are set up and the calculated values of CP(T) for copper nanoparticle are fairly consistent with the experimental ones. A relationship between Debye temperature and density of nanocrystalline is proposed, and Debye temperature can decrease with the reduction of nanocrystalline density. The calculated values of CP(T) of copper nanocrystalline are also quite consistent with the experimental ones. The bulk modulus of elasticity of nanocrystalline will drop off with the decrease of grain size of nanocrystalline, which should be taken into account when the CP(T) of nanocrystalline is calculated. The calculation methods proposed in this paper are feasible.