Abstract: The paper is an experimental study of retroactive inhibition by applyingregressive-rotatable design, A significant effect was obtained from the experi-ment which proved second-order equation was fitted to the data. The experi-ment showed that the degree of original learning lists (A) and the length pfinterpolate lists (C) played the main role in the four factors concerning theeffect of retroactive inhibition. When A was satisfactorily adequate, the retro-active inhibition, relatively speaking, was always minimal, whether C waslong or short. Whan A was satisfactorily adequate, the length of C and retro-active inhibition exhibited functional relationship of direct proportion. Thisstudy successfully manifasted that regressive-rotatable design is applied notonly to psychological studies, it also can show the functional relationship ofpsychological phenomena which changed under the total effect of multifactors.Hence it has taken a step forward than the methods of traditional design inpsychology.

Key words: regressive-rotatable design, retroactive inhibition, design variable, parabolae, rising ridge