Abstract: Abstract This paper describes an analysis method for isotope tracer 35S-KSCN and its test in oil field, Investigated an extraction method for 1L 35S-KSCN sample from oil field. Through condition experiment, the sample from oil field including minim 35S-KSCN could be extracted quantitatively at the range of acidity of 0.5-2.0mol/L HCl with TBP. 35S-KSCN was determined with a liquid scintillation counter, the minimum detectable limit for 35S-KSCN is 0.02Bq/L, the chemical recovery of this method is above 90%., the linearity relation is good from 0.02Bq/L to 5Bq/L. Through the test in oil field, get ideal data, validate this tracer is ideal tracer in waterflood reserves, at same time it show this method is quite sensitive, simple and prompt. It can be used for inter well tracer test technology.