This paper presents the discussion on a method of measurement of height by SEM and its resuits，in takmg the case of some Miocene diatoms. If the stereomicrographs are taken，it is easy to calculate a three-dimentional height from the following formula：H＝b/sinθ-a/tanθ（θ is the angle between a stereopair. A and b are the distances of the specific points from the axis of rotation.).As the results，the inner depths of the frustules of Thalassionema andDenticulopsis，and the relative relief of the frustule surface of Actinocyclus are quantitativeiy clearified These values must serve to deepen our understanding on the outer micro-features，though the slight aberrations are undevoidable.