Origin of life and evolution, early life on Earth and the global climate changes are among the major concerns because of their close relations with human beings. X-ray spectrometry (X-ray fluorescence and X-ray absorption) plays an important role in making scientific discoveries by determination of the elements and their species. In the review, we demonstrate the application of XRS to the studies in the origin of life, the identification of life traces on the early Earth and the global climate changes. Major reviews are on (1) how the analyses of C, Fe and S species are used in interpreting their roles in the hydrothermal vents and the RNA world; (2) what are the difficulties in the identification of early life and can be done by the determination of stromatolite, minerals with disproportionation reaction and organic microfossils in the identification of biogenic and abiogenic process; (3) what are the correlations among Fe sources, the species, organic matter and the bioavailability in the carbon circles in the oceans and the inland water systems.