The hot carrier dynamics of Zn0.91Cd0.09Se/ZnSe multi-quantum wells were studied using the femtosecond time-resolved photoluminescence upconversion technique. The carrier cooling behavior was investigated for different compositions at various lattice temperatures. The hot carriers generated photoexcitation by 405nm Ti:sapphire laser pulses release their excess energy primarily through carrier-LO-phonon interaction. As the excess energy reduce to the amount that lower than the energy of LO phonon, the excess energy was released by carrier-TA-phonon scattering before radiative recombination occurs. We have determined the scattering times of carrier-LO-phonon scattering at different lattice temperatures. No hot phonon effects was found at low photoexcited carrier density. The dependence of photoluminescence lifetime on wavelength was also discussed.