Carrier recombination through radiative and nonradiative processes in lattice-matched n-Zn0.5Cd0.5Se/Zn0.21Cd0.19Mg0.6Se multi-quantum-wells (MQWs) was investigated by temperature-dependent time-resolved photoluminescence (PL) spectroscopy. The n-Zn0.5Cd0.5Se/Zn0.21Cd0.19Mg0.6Se MQW samples with different well widths were grown on InP substrates by molecular beam epitaxy. The PL decay times and the PL intensities were measured as functions of temperature. For a doping level of 1×1018 cm-3, the dominant mechanism of the radiative process was found to be free carrier recombination while excitonic recombination was absent due to the effect of strong carrier screening. The nonradiative mechanism was determined to be hole capture through multiphonon emission (MPE). The expressions of the nonradiative MPE recombination lifetime, the PL decay time, and the PL intensity were deduced as functions of temperature and were used to fit the measured temperature dependence of the PL decay times and the PL intensities. The MPE activation energies and relative defect densities for the samples with different well widths were obtained. A simple method is suggested to investigate the interfacial defects of quantum wells.