The study is about the threaten of soil salt in Song Nen plain. We prognosticate through fixed-point and fixed-position from 1996 to 2000. And the soil salt of only irrigation and not drainage is above irrigation and drainage. The average soil salt of only irrigation and not drainage is 0.1086%, the average soil salt of irrigation and drainage is 0.1004%. In the finally we find out soil -salt contain and exercise regulation, the report is brought up about the degree of soil salt and its developing trend, at the same time the way of preventing soil secondary salinization is brought up.