Abstract: In order to investigate the effect of hydrogen content on thermoacoustic coupling in micromix combustion, this paper conducts experimental studies on combustion thermoacoustic instability under different hydrogen-methane ratios. The time-averaged and transient flame structures of flames with hydrogen contents ranging from 0% to 100% are studied through the flame structure, and dynamic characteristics are studied through the dynamic pressure. Time lag analysis method is performed to analyze the thermal acoustic coupling characteristics. The results show that thermoacoustic instability occurrs at the operating point with a hydrogen content of 10%, and a large area of blowoff and reignition occurrs at the root of the flame, resulting in a drastic change in the flame lift-off distance. Theoretical analysis shows that at the operating point with a hydrogen content of 10%, both the first order acoustics longitudinal natural frequency of the burner and the time lag condition required by the Rayleigh criterion are reached, meeting the condition when thermoacoustic instability occurs. In this study, the chemical reaction time lag accounts for at least 65% of the total time lag, indicating that the chemical reaction time lag plays an important role in thermoacoustic oscillation analysis. Factors such as preheating temperature and equivalence ratio that affect the chemical reaction time lag have a significant impact on thermoacoustic instability. The research results of this article can be used to guide the design of micromix burners for passive control of thermoacoustic instability through time lag adjustment.