Abstract: Through a new model of triangular heterosis based on the preliminary construction of the project team, this study selected the representative inbred lines of three heterosis groups including Y 46, Y 107 and MON 2 from the Group Suwan 1, Group Reid and Group Non-Reid to construct six advanced generation backcross populations(namely BC₁F_7∶8) and investigate into the genetic difference and heterosis of leaf morphological traits including leaf length（LL）, leaf width（LW） and leaf angle（LA）. The results showed that there were significant differences in LL, LW and LA traits among six BC₁F_7∶8 populations. The leaf morphological traits of BC₁F_7∶8 populations of Y 46 to Y 107 were higher than those of Y 46 to MON 2 and Y 107 to MON 2. What’s more, there were relatively big difference in each trait between crossing and reciprocal crossing populations combined by Y 46 to MON 2. As for the heterosis, the leaf morphological traits of the Y 107 to MON 2 populations was strongest, and the BC₁F_7∶8 populations derived from Y 46 and MON 2 was inferior. The combination Y 46 to Y107 populations were between the above two. This means that the heterosis of leaf morphological traits of Reid to Non-Reid was strongest, Suwan 1 to Reid ranked at the middle, and Suwan 1 to Non-Reid was inferior in the triangular heterosis group pattern. Therefore, the heterosis pattern of Reid to Non-Reid should be the principal choice to cross for screening ideotype maize hybrids with resistance to high-density in breeding program.