Abstract: Single case research design is suitable for raising research hypothesis, and the clinical confirmation of this hypothesis can be gained by other methods afterwards. It is also suitable for the pilot study, which carries on a preliminary assessment to the medicine that will be studied before designing and planning the formal clinical study. The classification of single case research designs includes simplest single-case design, classical reversal design, alternating-treatment design, and multiple-baseline design. The premise of this design is that the treatment can display the most remarkable effect in a shorter time, and the effect is temporarily, once the treatment is stopped, the patient' s condition is reversed. Otherwise, the group design must be considered. Generally, the approach of single case research depends on the “A” stage of stable baseline phase. It means that this research approach is not suitable for carrying on research to the acute or inconstantly diseases, but suitable for carrying on research to the chronic or recurrent diseases which have stable manifestations.

Key words: single case research designs, simplest single-case design, classical reversal design, alternatingtreatment design, multiple-baseline design