A systematic investigation on the effects of type of compatibilizer precursors (CP) upon the barrier properties and morphology of PE/PA blends was reported. Three alkyl carboxyl-substituted polyolefins were selected td modify PA in a twin screw extruder by "reactive extrusion" process. The barrier property of the modified PA (MPA) was better than pure PA, and the amount of barrier improvement of the blend of PE and MPA depended significantly on the barrier property of the MPA prepared. The extent of mixing PE and MPA before blow-molding has a significant effect on its corresponding barrier properties. Further analysis of the fracture surfaces indicated that a more demarcated laminar structure of MPA dispersed in PE matrix is essential for better barrier properties of PE/MPA blends. It is not completely clear how the type of CP added affects the barrier properties of MPAs. However, it is suggested that long PA sequence with shorter grafted CP chain and high normalized grafting efficiency of MPA are essential for preparing a clear laminar structure of MPA, and a good barrier properties of PE/MPA blends.