In this study, the effects of hydrogen co-firing rates and thermal power variations on combustion instability were analyzed in a single burner combustion test rig, using CFD and 1D network modeling techniques.the time delay and its distribution in a flame zone derived from CFD were applied to the network model in order to evaluate the combustion instability characteristics.The analysis results confirmed that the key modeling characteristics closely matched the experimental measurements.Consequently, we verified that the increase in hydrogen co-firing rates and thermal power significantly influence the time delay and its distribution, and that these changes are the primary causes of alterations in combustion instability characteristics. CFD 1D .CFD time delay time delay distribution , . , . time delay time delay distribution , .