We derived crystallization conditions of amorphous silicate by comparing theoretical model with three different kinds of crystallization experiments: annealing experiments of (1) an amorphous silicate with forsterite composition, (2) an amorphous silicate covered with a carbonaceous layer, and (3) an amorphous silicate covered with a carbonaceous layer consisting of reactive molecules (e.g., CH_4). From the experiments (1) and (2), we obtained the activation energies of diffusion in the amorphous silicate and amorphous carbon. From these values and the comparison with the experiment (3), we derived the constraints on the energy density stored in the mantle layer and the chemical reaction time to occur the crystallization of amorphous silicate.