Abstract: The a analogitiy of fast transient heat conduction and mass diffusion is analyzed in physical mechanisms and mathematical formulations etc. Theoretical and experimental results both indicate the fast transient heat conduction and mass diffusion have analogous physical behavior-fluctuation mechanism and same mathematical formulations. The dimensionless numberand H_h and H_m, as well as their effects on the distributions of temperature and concentration are given out by theoretical analysis and nuxnerical simulation. Meanwhile, the dimensionless number H₁ (H₁=\fracH_hH_m) is also defined, which reflects the identical extent of temperature and concentration distributions.