The mixed-level designs have become widely used in the practical experiments.When the levels of some factors are difficult to be changed or controlled,fractional factorial split-plot (FFSP) designs are often used.It is highly to know when a mixed-level FFSP design with resolution Ⅲ or Ⅳ has clear effects.This paper investigates the conditions of a resolution Ⅲ or Ⅳ FFSP design with both two-level and four-level factors to have various clear factorial effects,including two types of main effects and three types of two-factor interaction components.The structures of such designs are shown and illustrated with examples.