The Australian love of "heritage" buildings (most of them are unreinforced masonry (URM)) means that greater attention is required to secure their performance under seismic or impact loading in the future.A research project has been carried out to develop a new,economic and high strength retrofitting technique for masonry structures.A series of experimental testing on URM walls retrofitted with an innovative technique by cable system have been conducted.In this paper,an analytical model which is based on distinct element method(DEM) is developed to simulate the behaviour of retrofitted walls.In DEM,a solid is represented as an assembly of discrete blocks.Joints are modelled as interface between distinct bodies.It is a dynamic process and specially designed to model the behaviour of discontinuities.In order to assist the practising engineers to design this new retrofitted wall system,a simple mechanical model was also developed to predict the strength of the retrofitted walls.The results obtained from this simple mechanical model are compared with those from both experiments and distinct element model.