Abstract: On the bests of study of geochemical behavior of sin81e elements,the paper has established a mathematic model for linear relationships between elementS in the chemical sedimentary process of a semi-closed system:which is very similar to that of magmatic fractional crystallization (Wan Yusheng, 1990).In the formula, C C and C C represent the contents of elements x and y in original saturated solution and reSidual satuxated solution respectively, D_x and D_y are bulk distribution coefficentS of x and y ,Fi is reSidual ratio of saturated solution, and t is solute proPOrtion in saturated solution.Example shave also been given to show how to apply the method to research on saline sedimentation.Following are some main conclusions:1) The regression line representS the result of the linear regression of a cutve with lesscurvature.Foe an incompatible element-fair, the more similar the properties of two elements andthe smaller their bulk distribtition coefficientS are, the better the regresion line is.2)The nit6rcept and slope of the regression line have clearly geochemical significance.Both ofthem are constituted by the P8rametCrs C,C, D_x, D_y, t and Fl.If x and y are incompatible, then the slope of the line will be active and the line will intersect a relatively compatible element axis.When D values of x and y are similar, the intercept and slope of the regression line are close to zeroand C/C respectively.3)There could be different degrees of linear correlations between two elements of elementpair at different stages of evolution of the saline water, resulting from asynchronous variations ofthe bulk diStribution coefficients of the elements.And in different saline water systems, the sameelement-pairs can represent different degrees of linear correlations, so the chemical compositions of the systems will strongly influence the geochemical behaviors of the elements.