The numerical simulation is carried out to investigate the cold fluid field characteristics of small pylonaided gaseous fuel injection with six different port shapes in the supersonic combustion. The result shows that pylon can raise mixing efficiency and fuel penetration height without big total pressure loss. The pylons combined with square, circular and triangle port nearly have the same flow characteristics, but with diamond port and jet of rectangle 10:1 can get remarkable mixing enhancement. A high aspect ratio injector can get the advantages of low pressure and high vertical magnitude depression behind the pylon, which is much better than the no pylon cases. Through the investigation, a better understanding of the characteristics of flow field with pylonaided fuel injection is made, and the investigation supplies optimization of injector with basis.