The crystallization behaviors of binary even-even normal alkane (n-alkane) mixtures (n-C18H38/n-C20H42 abbreviated as C-18/C-20) with different Compositions, both in the bulk state and in nearly monodisperse microcapsules, have been investigated by the combination of differential scanning calorimetry and temperature-dependent) X-ray diffraction. The solid-solid phase separation, usually observed during the cooling process of bulk samples, is greatly suppressed and even eliminated after being microencapsulated, with the orthorhombic-ordered phase dominating in the low-temperature crystal. Such a crystallization transition is attributed to the special interaction between the two even n-alkanes and the confined environment in microcapsules. The triclinic ordered phase, solely formed by the single even n-alkanes (C-18 or C-20), becomes less stable due to the weakening of the layered structure and the suppression of the terminal methyl methyl interactions in the confined geometry, which favors the miscibility of the two components. Furthermore, besides the chain-length difference and the composition, the confined environment is proved to be another important factor to exert strong positive influence on suppressing the solid solid phase separation of C-18/C-20 binary System.