Abstract: The Madden-Julian Oscillation(MJO) is a dominant mode ofintraseasonal variability in the tropical atmosphere;it is characterized by an eastward propagating tropical convective anomalies and associated with circulation anomalies with a time period between 30 to 60 days.Since Madden and Julian firstly observed the MJO (Madden and Julian,1971),it has been extensively studied in the past decades.Studies suggested that the MJO has a baroclinic mixed Kelvin and Rossby wave structure in the Indian and the western Pacific Oceans,where the equatorial wave is strongly coupled to convection with eastward propag ation in convection atroughly 5 m/s. Kelvin waves propagate eastward out of the convective regions is at phase speeds of 10~12 m/s(Hendon and Salby,1994),and is generally manifested as an east ward propagating,equatorialy-trapped,wave number one,baroclinic oscillation in the tropical wind field (Madden and Julian,1994).