AZ91D magnesium alloy was processed by equal channel angular extrusion(ECAE).The influence of extrusion temperature,extrusion pass and extrusion route on the ultimate strength of the extruded billet was analyzed.The process of multi-pass extrusion was simulated with the method of finite element analysis,and the continuity and uniformity of effective strain in multi-pass extrusion were investigated.The results show that extrusion pass plays the most important role in improving the ultimate strength of AZ91D magnesium alloy,the extrusion route is the second,and the extrusion temperature is the last.From the numerical simulation,there exists the continuity of the accumulated deformation in multi-pass extrusion and the effective strain increases linearly.The tendency of the strain uniformity is different in multi-pass extrusion with extrusion routes.The results of experiment agree with those of numerical simulation.