To accurately and promptly obtain the conventional lifetime of light-emitting diode (LED) lights, accelerated degradation tests of LED lights under four groups of accelerated stresses were designed and carried out. Three-parameter Weibull function and the right approximation method were used to fit the average luminance degradation test data at each constant accelerated current stress. Combined with the failure criteria, the service lifetime of the samples under each accelerated stress condition was calculated. Then, four groups of accelerated degradation data points were extrapolated by power function and exponential function respectively, and the average lifetime of LED lights was calculated, thereby achieving the estimation of conventional lifetime. The results show that the luminance degradation rate of LED lights is initially fast, then slow, which accurately represents the basic rule of luminance decay. The model established by the Weibull right approximation method exhibits high fitted accuracy for the luminance degradation data of LED lights. By comparing the determination coefficients and the mean absolute percentage errors of extrapolation, it can be found that the conventional lifetime extrapolated by power function has superior accuracy, satisfying the actual project requirements. The relevant research results can provide technical support for the life prediction of LED lights.