The creep damage in high temperature resistant titanium alloys Ti60 is measured using the nonlinear effect of an ultrasonic Lamb wave.The results show that the normalised acoustic nonlinearity of a Lamb wave exhibits a variation of the "increase-decrease" tendency as a function of the creep damage.The influence of microstructure evolution on the nonlinear Lamb wave propagation has been analyzed based on metallographic studies,which reveal that the normalised acoustic nonlinearity increases due to a rising of the precipitation volume fraction and the dislocation density in the early stage,and it decreases as a combined result of dislocation change and micro-void initiation in the material The nonlinear Lamb wave exhibits the potential for the assessment of the remaining creep life in metals.