The present invention relates to a supported metallocene catalyst used for preparing polyolefin whose physical properties and molecular weight distribution can be easily controlled, a method for preparing the same, and a method for preparing polyolefin using the same, more particularly to a support metallocene catalyst wherein at least two kinds of metallocenic transition compounds are supported on a metal oxide such as silica, a method for preparing the same, and a method for preparing polyolefin using the same.