The electron-LO phonon scattering rate of the first excited state to the ground state in Cd1-xMnxTe/CdTe quantum well is calculated theoretically based on Fermi golden rule, and the variation of average scattering rate with the well width, temperature and Mn component is also discussed. Results show that the electron-LO phonon scattering rate decreases gradually with increasing of the total initial energy. The scattering rate and mean scattering rate increases up to their maxima which appears at 20 nm of the well width, then begins to decrease as the well width increases. When quantum well width is greater than 20 nm, the ‘cut-off’ will occur in scattering. The scattering rate and mean scattering rate increase monotonically with increasing of temperature. In the case of low temperature, the variation of mean scattering rate is not obvious, but it changes distinctly when the temperature is relatively high. The mean scattering rate of electron-LO phonon in quantum well decreases with increasing of Mn component.