Abstract:The study focus on the liberating condition for the sulfide in soil, that the addition of the reduced materials into the reaction system and the certain change of result. the calculation of acid concentration and its application, the statistic of accuracy and the precision. the study purpose is to provide with a conference for the sulfide liberating undone, in this experiment ,EDTAna2 and Vc are also used in order that both the interferences can be deliminateed and recovery rate will be done well ,with addition of sncl2,the amount of sulfide liberated from spil increases ,spiking recovery also gets better by 5%-10%.the precision for three types of soils is 5.58、6.12、10.1.recovery rate is 77.8%、81.9%、64.4%. the some metal sulfide and the soluble sulfide can be liberated and calculated accurately without fault.