Abstract: In order to study the relationship between 1 nm manganate and 0.7 nm manganate,a series of S1nm M²⁺ manganates are made after the synthetic lnm manganate (S1nm Na⁺) substituted with the different kinds of divalent canons.The X-ray deffraction analysis of S1nm M²⁺ manganates when they are wet and after 24 h room temperature dry shows their quite different characteristics of the d-spacing and indicates that there are phase changes between 1 nm manganate and 0.7 nm manganate.Those lnm manganates with unstable layer structure will collapse to 0.7 nm manganate by tossing one inter layer OH-H₂0 after RTD,while those with stable layer structure will still remain their lnm d-spacing.This fact reminds us that the samples of manganese nodules must be kept in wet when we do the mineral analysis to avoid the uncorrect results.The structural stability of lnm manganate is mainly controlled by the interlayer divalent cations such as Cu,Co and Ni.There is positive relationship between the interlayer contents of the divalent cations and their structural stability,while the capacity of different cations in stabilizing the layer structure of lnm manganate is as follows:Ni>Cu>Co>Zn>Ca>Mg>Na.