An in-situ Raman Spectroscopic study was conducted to explore the pressure-induced phase transformation of CaMn 2 O 4 to pressures of 73.7GPa. Group theory yields 24 Raman active modes for CaMn 2 O 4 , of which 20 are observed at ambient conditions. With the slight compression below 5GPa, the pressure-induced contraction compensates the structural distortion induced by a Jahn-Teller (JT) effect, resulting in the occurrence of the zero pressure shifts of the JT-related Raman modes. Upon elevation of pressure to nearby 35GPa, these Raman modes start to display a significant variation in pressure shift, implying the appearance of a pressure-induced phase transformation. Group factor analyses on all possible structure polymorphs indicate that the high-pressure phase is preferentially assigned to an orthorhombic structure, having the CaTi 2 O 4 structure. The cooperative JT distortion is continuously reduced in the CaMn 2 O 4 polymorph up to 35GPa. Beyond 35GPa, it is found that the JT effect was completely suppressed by pressure in the newly formed high-pressure phase. Upon release of pressure, this high-pressure phase transforms to the original CaMn 2 O 4 phase, and continuously remains stable to ambient conditions.