Some analyses on intraseasonal oscillation in the tropical atmosphere are completed by using the ECMWF data. The results show that there are two kinds of the disturbance pattern, Kelvin wave like and Rossby wave like, in tropical intraseasonal oscillation. The disturbance pattern and the anomaly of the cumulus convection are fundamental factors to affect zonal propagation of tropical intraseasonal oscillation. Accompanying the occurrence of El Ni?o event, the kinetic energy of intraseasonal oscillation in the tropical atmosphere decreases rapidly and the kinetic energy of the quasistationary disturbance increases rapidly, this means the exciting effect of tropical intraseasonal oscillation to El Ni?o event and represents a cause for weaker intraseasonal oscillation during El Ni?o event.