An in vitro acid-resistant and remineralized study on human root surface with 500ppm lanthanum,Cerium and Fluoride accidulate buffer was carried out in a pH-cy-cling system.The results of quantitative chemical and energy spectrometry analyses showed that all these three elements had the demineral-resistant effects,although fluoride showed a better effect,Furthermore,the mechanisms of lanthanum,Cerium and Fluoride on demineral-resistant were discussed from the viewpoint of crystal physicochemistry.