Polar surface dominated Sn doped ZnO nanowires (NWs) with an octagonal shaped cross section have been fabricated by chemical vapor deposition method. The NWs grew along [01 (1) over bar0] direction, and were wrapped by non-polar surface (2 (1) over bar(1) over bar0) and polar surfaces (0001) and (10 (1) over bar1). Planar defects in (0001) plane were formed in the middle of the doped NWs, and strain concentration occurred around the planar defects, which might lower the energy in the wurtzite lattice and thus maintain polar surface dominated configuration. X-ray photoelectron spectroscopy (XPS) and Raman tests reveal that the concentration of Oxygen vacancy (V-O) was significantly lowered after doping, which led to the reduced deep level emission (DLE).