The radiative transition and nonradiative process have been studied for Ho3+ ions in ZnS semiconductor. From the integrated emission intensity and excited state lifetime, the intensity uarameters of ZnS:Ho3+ were obtained and radiation probabilities and lifetimes of Ho3+ ion's nine energy levels were calculated. Nonradiative process among 5G6,3K8,5F2,5F3 and 5S2 ( 5F4) was investigated by measuring the emission intensity and fluorescence lifetime at differenttemperatures. 5G6, 3K8, 5F2 and 5F3 are in thermal equilibrium and there are 5 phononsparticipating in the multiphonon relaxation between 5F3 and 5S2( 5F4).