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CrTe₂ is a novel magnetic layered transition metal dichalcogenide that has been recently synthesized in a metastable 1T bulk phase with a high-curie temperature of 310 K. While its 1T phase has been investigated both experimentally and theoretically, detailed theoretical studies on the other possible phases and phase transition are imperative. In this work, we studied the structural, electronic, and magnetic properties of 1T, 1H, and 2H phases of CrTe₂ using density functional theory (DFT). The 1T phase of CrTe2 was found to be the ground state in both bulk and monolayer structures at low temperatures. The energy barriers of the phase transition between the 1T, 1H, and 2H phases were calculated by the Nudge Elastic Band (NEB) method. By applying the linear response method, we obtained the self-consistent U parameters in 1T, 1H, and 2H phases of CrTe₂. The 2H and 1H phases were predicted to be metallic and ferromagnetic with DFT+U correction, which is in contradiction to previous theoretical studies.