A mathematical model for the unsteady state heat and mass transfer in regenerative rotary heat exchanger is derived and solved numerically by using finite difference method. Triangular shape of the rotary matrix with silica gel (SiO2) that used as desiccant material is taken here. The heat transfer coefficient and the mass transfer coefficient that used in the present study are suitable for different types of the matrix shapes. The unsteady state time effect, inlet air temperature, Number of Transfer Unit (NTUt), heat exchanger length, inlet air temperature and the desiccant material volume on the latent, sensible and total effectiveness are discussed. It has been notes that the increasing of the heat exchanger length, inlet air temperature, desiccant material volume and the (NTUt) will increase the sensible, latent and total effectiveness. The increasing of the inlet air mass flow rate will decrease the total, latent and sensible effectiveness. The steady state time for the latent effectiveness is lower than the steady state time for the sensible and total effectiveness.