The Generalizability Theory( GT) and Item Response Theory( IRT) are two main modern measurement theories and widely applied in psychological measurement and evaluation. However,both theories have advantages and disadvantages. Therefore,GT and IRT should be integrated by means of adhesion or fusion. Comparing to the adhesion,the fusion can produce a new model,which can make two theories towards one unity and complement each other and have obtained a strong advantage. The present study showed five fusion models of GT and IRT such as the Multivariate Modeling approach( MM),Hierarchical Rater Model( HRM),Generalizability in Item Response Modeling( GIRM), GIRM for Testlet( GIRMT) and some other fusion models.Some proposals about these fusion models were also proposed.