Abstract: The unusual typhoon tracks, such as turning northward and westward and recurving and looping, that occurred in foureen typhoons and severe tropical storms over the North western Pacific Ocean in 1990, are studied using CMS enhanced IR imageries and OLR from NOAA-11. The results show that: (1) the asymmetric distribution of typhoon cloud system caused by mesoscale convective activities around the typhoon center leads typhoon movement. When the mesoscale convective activities apper in its southern to northeastern or northern sector, typhoon would move northward. When they appear in its western or southwestern sector, typhoon would turn westward, when they appear in its eastern or northeastern sector and the cloud system of a cold front or Subtropical jet stream joins the northern part of the typhoon cloud system, the typhoon would recurve northeastward. (2) The direction of the axis in lower OLR area around the typhoon center and its variation is closely related to the movement of the typhoon and the coefficient of correlation is up to 0. 83.All these above may contribute to better understanding unusual typhoon movement and improving its nowcasting and warning.