To know more altitude compensation and base characteristics of plug nozzle, cold-flow tests on 1-cell 2D linear plug nozzle, which utilize high pressure air as propellant were conducted. The effects on 1-cell 2D linear plug nozzle of base wall and base bleed ratio were studied. The pressure distribution on plug was also studied. The results indicate that the performance of plug nozzle can be increased 2%~7% without base wall at low altitude. The bleed can increase base pressure and decrease the variety of thrust which be caused by changing from open base to close base. It is found that 1% to 1.5% base bleed ratio is the optimum value range and the performance of plug nozzle would be decreased if base bleed ration is more than that range. The maximum nozzle efficiency of all of plug nozzle tested here are more than 99%, some of them are nearly 100%. It has good altitude compensation.