Abstract: The evolution equation of planetary wave and inertial-gravity waves are ob-tained from the anelastic equations based on a weakly nonlinear assumption. nomthe resonance surface and increase rate curve, it is found that the planetary waveprefers to interact with large scale inertial-gravity waves. By using the equivalentgravity wave assumption of tidal wavest the interaction among the typical 2 daysplanetary wave, semidiurnal tide and 9.6 hours inertial-gravity waves are investi-gated in detail. The exchange of energy between planetary wave and semidiurnaltide is found to proceed more strongly than the exchange between them and the9.6 hours inertial-gravity gravity. The variability of tidal and planetary wave am-plitudes may be caused by nonlinear interaction between them.