AbstractSmall Punch tests (SPT) have been performed on four different zones of P91 welded joint, namely the base metal (BM), the weld metal (WM), the heat affected zone at base metal side (HAZ-BM) and the heat affected zone at weld metal side (HAZ-WM). Besides the creep rupture times, full creep deflection curves are also available from which creep properties of different HAZ zones can be derived.In this paper, an analytic approach, based on Chakrebarty’s membrane stretch model and Kachanov’s creep law, is used to interpret the creep deflection curves of different zones. First, strains and stresses are derived from the observed deflection curves according to the Chakrebarty’s membrane stretch model, then the Kachanov’s parameters are determined by attempting to minimize the sum of the squares of the residuals (difference between derived strains and calculated strains at each time point). With Kachanov’s parameters known, all creep properties can be obtained.