Abstract: The influence of steam injection into combustor on combustion efficiency and pressure loss in the combustor is investigated.The testing was conducted with a WZ 5 gas genarator burning low BUT gaseous fuel (H uv =8172kJ/N·m 3).The steam injection was arranged in either the diffuser or the dilution zone of the combustor.The test results show that the steam injection has only a little effect on combustion efficiency and a considerable effect on pressure loss.In the case of the ratio of steam flow rate to air flow rate being 10%,the steam injection into dilution zone would cause an 12% increase in pressure loss,and even larger than that the steam injection into diffuser would cause.