This article compares case study and single subject research from four aspects: the concept, characteristics, process, and study design. And finally it sums up the following conclusions: (1)These two research methods both have the advantages and disadvantages of single case study, and are suitable for the small sample size and sample heterogeneity larger research: (2)Case study tend to qualitative research, single subject research, on the other hand, tend to quantitative research; (3) Case study have problems in scientific and normalization;(4) The application of single subject research is ver...