Abstract: In order to achieve the goal of low emission for gas turbines, the combustion instability characteristics of spiral micro-mixing-swirl composite nozzles under different hydrogen mixing ratios were experimentally studied. Under constant output power, the pressure oscillation state of combustion chamber and precombustion stage in the range of 0%-100% hydrogen mixing ratio was investigated. Results show that under equivalent ratio of main combustion stage of 0.45, the amplitude of pressure oscillation in the combustion chamber increases first and then decreases with the increase of hydrogen mixing ratio. When the hydrogen mixing ratio is 70%, two frequency pressure oscillation signals of 2 903.4 and 4 490.2 Hz appear in the combustion chamber. The two frequency pressure oscillations produced by the combustion at the hydrogen mixing ratio coincide with the natural acoustic mode frequencies of the combustion chamber, and then form standing waves. The first-order acoustic mode frequency of the precombustion stage is 5 450 Hz, and the sound waves in this frequency band generated by the combustion zone propagate to the precombustion stage to form standing waves, resulting in the peak pressure pulsation near 5 400 Hz in the precombustion stage. In contrast to the combustion chamber, the pressure pulsation amplitude is the smallest under the 70% hydrogen mixing condition. Considering the pressure pulsation of combustion chamber and precombustion stage, it is considered that the optimal hydrogen mixing ratio of main combustion stage is in the range of 30%-60%.