The comprehensive analysis about heat-generating processes is presented in Er:tellutire glass. The heat fraction of each process and total heat fraction during pumping are investigated. The results show that upconversion is an important heat-generation process and heat problem is serious especially at high Er 3+ doping level. The influence of pump power on heat fraction is also discussed. Based on the heat analysis, the optimized doping concentration range of Erbium ions is about 0.5 mol% to 1.0 mol%.