A t hree - dimensional FEM model of rotary draw bending of t hin - walled rectangular tube is built under t he ABAQUS/ Explicit environment . Based on t he model , a simulation and analysis of rotary draw bending for aluminum alloy 3A21 thin - walled rectangular t ube have been carried out. The result s show t hat t he maximum height of wrinkling wave decreases obviously with the increase of the initial lead of t he mandrel, t he maximum tangential compress st ress and t he equivalent st ress de2 creases gradually, and t he variation become steadier. The maximum height of wrinkling wave does not almost alter wit h the increase of t he initial lead of t he mandrel when t he initial lead reached a fixed val2 ue. The achievement s of t his study provide a guideline for determining the process parameter s for t hin - walled rectangular t ube in rotary draw bending p rocess.