With absorptance spectra of platinum ions; relationship between platinuminclusion density and platinum redox equilibrium in R2O-BaO-P2O5 system phosphate laserglass was investigated. The results show that platinum inclusion density reduces as theequilibrium shifts towards right.With the melting temperature or OZ perilalpressure of melting atmosphere increased, the equilibrium shifts towardsright. When is large enough, platinum inclusions can not be formed.