Abstract: An improvement on the parametrization of wind stress is made to the tropical air-sea interaction model formerly proposed by Chao and Zhang: In this air-sea coupled model, the inertial-gravity waves are filtered out and only the equatorial Rossby waves are reserved in both the atmosphere and the ocean. Results indicate that after the air-sea interaction, two kinds of waves appear in the coupled model, one is of high-frequency and another is of low-frequency. The properties of the low-frequency waves are similar to those in Ref. 1. The different results from those in Ref. 1 are that besides the low-frequency unstable waves the high-frequency waves are unstable in the scope of comparatively long wavelengths. The stronger the air-sea interaction, the larger the amplifying rate and wider the scope in which the unstable high-frequency waves appear. This paper also proves that the physical condidons for the producing of the low-frequency and high-frequency unstable waves are different.