The invention discloses a multiscale prediction method of hardening normal cement neat paste thermal diffusivity. The multiscale prediction method of the hardening normal cement neat paste thermal diffusivity comprises the following steps: starting multiphase and multiscale division based on a microcosmic structure and a composition of the hardening normal cement neat paste, containing typical phase at each scale, then calculating size percentage of different phases, and calculating and acquiring early age cement neat paste thermal diffusivity by upward gradual homogenization and a generalized self-consistent method based on the size percentage content of each phase on each scale.The multiscale prediction method of the hardening normal cement neat paste thermal diffusivity considers the influence of the hardening normal cement neat paste microcosmic structure and the performance of the composition materials to the cement neat paste generalized thermal diffusivity, influencing factors which are considered are comprehensive and reasonable, simple in form, and convenient to use. A prediction model which is established based on the multiscale prediction method of the hardening normal cement neat paste thermal diffusivity can accurately predict the thermal diffusivity with different water cement ratios and different categories of the hardening normal cement neat pastes.