Previous research had proved that concentration of elements and compositions of isotopes in dolostone will reassign during the burial diagenesis in open system but no any principle for interpreting the rules is available yet. Chemical equilibration rules were employed and figured out that it is the ion radius that controls the reassigning of elements and isotopes during diagenesis. According to the principle, associated with the radius values of +2-valenced Ca, Mg, Fe, Mn and Sr ions, we can make deductions as following: 1) The dolostone order will increase during diagenesis; 2) the Fe and Mn concentrations in dolostones will be increase but Sr content will decrease and the ratio of isotope 87Sr/86Sr will increase during diagenesis. All of the deductions were supported by previously published data.