According to nonlinear finite element theory and basic assumption,considering both material and geometrical nonlinearity,Fortran language was used to compile nonlinear finite element analysis program , which was utilized to compute nine unbonded prestressed concrete test beams, about the ultimate bearing capacity of unbonded prestressed high performance fly ash concrete beams. The result of computation broadly accord with that of the test,so the analysis program was reliable,besides, it accurately and reliably forecast the whole process of structural response from load to damage about unbonded prestressed high performance fly ash concrete beams.Meanwhile the result of test shows that the differences of fly ash contents and intensity of concrete hardly have an effect on intensity of high performance concrete,and it also indicates that the parameters of concrete,steel and reinforce steel referring to General Code for Design of Highway Bridges and Culverts,eventually, achieve satisfactory results in the course of computation.