This study presents relations between the time lag and interaction index of the impinging-jet injectors using the time lag model in a model chamber. The response of the flame is analyzed to artificial perturbation with 5% amplitude of oxidizer speed at a resonance frequency. At the mixing point of fuel and oxidizer, which determines the characteristic length, the relationship between velocity perturbation and heat release rate is quantified by combustion parameters of interaction index and time lag. In this method, time lag or delay is calculated by the characteristic length and the average velocity obtained from numerical results. The tendency that the time delay decreases with axial jet velocity has been observed.