A time delay equation for the sea-air oscillator model is studied. The aim is to create an asymptotic solving method of nonlinear equation for the El Nino-Southern Oscillation model. And based on a class of oscillators of the model, employing the method of ENSO singular perturbation, the asymptotic solution of corresponding problem is obtained. It is proven from the results that the method of singular perturbation can be used for analysing the sea surface temperature anomaly in the equatorial eastern Pacific of the atmosphere-ocean oscillation for ENSO model.