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Long-range magnetic orders in atomically thin ferromagnetic CrI 3 trigger new fascinating physics and application perspectives. The physical properties of two-dimensional (2D) ferromagnetism CrI 3 are significantly influenced by interlayer spacing and stacking order, which are sensitive to the hydrostatic pressure and external environments. However, there remains debate on the stacking order at low temperature. Here, we study the interlayer coupling and stacking order of non-encapsulated 2-5 layer and bulk CrI 3 at 10 K by Raman spectroscopy; demonstrate a rhombohedral stacking in both antiferromagnetic and ferromagnetic CrI 3 . The opposite helicity dependence of A g and E g modes arising from phonon symmetry further validates the rhombohedral stacking. An anomalous temperature-dependent behavior is observed due to spin-phonon coupling below 60 K. Our study provides insights into the interlayer coupling and stacking orders of 2D ferromagnetic materials.