It has been found that temperature is a major factor that determines the creep properties and relevant mechanisms of spray formed (SF) superalloy GH742 in its deformed and heat treated fine grained version. The alloy has high creep resistance at 650 degrees C and low creep resistance at 750 degrees C. In order to observe the structural changes during creep, the samples for creep tests cut after and in the course of creep tests were studied by means of OM, SEM, TEM. The creep curves and properties tested and the observations made by TEM were summarized in this paper. Preliminary results show that under different test conditions, grain boundary and phases within the alloy jointly play a dominant role in creep properties and mechanisms.