"小样本连续研究法" can be translated into English as "small-sample continuous research method" or "longitudinal small-sample research approach".
"Small-sample continuous research method" directly conveys the idea of conducting continuous research with a relatively small number of samples.
"Longitudinal small-sample research approach" emphasizes the longitudinal (over-time) nature of the study while specifying the small sample size, which might be more suitable if the focus is on tracking changes or developments within the small sample over an extended period.
Both translations are acceptable, and the choice may depend on the specific context and emphasis of the research.