The invention provides a gas-steam generator provided with air outlet ports with density change. The gas-steam generator comprises a water tank and a combustor, wherein the combustor comprises a combustor seat; a plurality of air outlets supplying a combustion improver to a combustion head are formed in the combustor seat; an air supply channel communicated with the air outlets is formed in the outer side of the combustor seat; and the distribution density of atomization holes is reduced in the radial direction from the centre of the combustion head to the outside. According to the gas-steam generator provided by the invention, the gradual increasing of the number distribution of gas from the outside to the middle is ensured through the distribution density change of the atomization holes;and lots of gas is adequately combusted at the middle position, and combusted from the middle part during combustion, and then smoke is discharged from a reflow hole, so that the smoke can be used for heating by virtue of the whole heating surface, and the uniformity of integral heating is ensured.