Abstract: The stable isotope techniques (SIT) have been widely used in ecological research in which the ¹⁵N technique is the most effective in the research area of grassland nitrogen cycle.This paper reviewed research status and progresses for the ¹⁵N technique in the N biological fixation,fate and use efficiency,transformations and nitrogen loss in grassland ecosystem.And also addressed the problems and prospects in these studies,provide theoretical basis for the future researches to make better use of nitrogen and improve the grassland production.