Assorted morphologies of precipitates in fcc/bcc transformation systems have been reported, which often exhibit irrational characteristic. Various models have been developed to explain the habit plane (or the broad facet), but the overall morphologies of the precipitates are seldom explained quantitatively. In this work, the equilibrium cross-section of rod-shape austenite precipitates in duplex stainless steel is determined by atomistic simulation. The input orientation relationship (OR) between fcc and bcc phase is determined according to the O-line criterion (one of the interfaces contains a single set of dislocations), with the condition that the invariant line lies in close-packed plane pair of and the Burgers vector of O-lines is . The obtained OR is close to the K-S OR , , with the deviation of 1.27° from the parallelism in both planes and directions. Interfacial energy of interfaces in various orientations in the zone axis of the invariant line has been calculated. To ensure the reliability of the calculated values, an initial atomic configuration free of interstitial and vacancy is constructed for each interface. The energies of the O-line interface, the interface normal to either or Δg₍₀₂₀₎ are found to have similar values, each at a local minimum. Based on the calculated interfacial energies, the equilibrium cross-section morphology is determined by the Wulff construction. The result shows that the morphology exhibits a near rhombus cross-section, which agrees consistently with experiments. One of the major facets is the O-line interface, normal to , in agreement with the observation. The other facet is normal to Δg₍₀₂₀₎ in the calculated result, while it is normal to in experimental results, with about 10^o difference between them. The discrepancy between calculated and observed results is probably because the experiments have not reached the equilibrium state. The dislocation structures in these three interfaces are identified from the atomic simulation results by a newly developed method based on the singular value decomposition of the Nye tensor. It confirms that the O-line interface contains a single set of [011]_f/2 dislocations with spacing of 1.5 nm. The interface normal to either or Δg₍₀₂₀₎ contains two sets of dislocations. The dislocation structure in the facet normal to is in good agreement with experimental observation of the non-O-line facet, including the local decomposition of dislocation core to stacking faults.