Fe-S series,especially FeS2 and Fe1-xS is the main component of crustal rocks as important metal sulphides.Pyrite(FeS2) shows a promising vision in solar cell materials for its high absorption coefficient and suitable band gap.Predecessors have done some researches on the photovoltaic properties of Fe-S series under different conditions.However,little researches have been done on the coexisted sulphide of FeS2 and Fe1-xS.FeS2 and Fe1-xS often appear as symbiotically due to their similar formation conditions.So the study on the optical absorption characteristics of FeS2 and Fe1-xS are of important significance.In order to study the optical absorption characteristics of FeS2-Fe1-xS heterostructures,using the SEM and XRD to characterize the morphology,composition and structure,respectively.The results show that the samples were cubic pyrite with a certain amount of pyrhotite(Fe1-xS).The crystal partical size was between 5 and 10 nm.Measurement of the absorption spectrum was performed using Cary 500 UV-Vis-NIR spectrophotometer,acquiring the results of 1 860～1 889 nm,and the absorption peak in 1879nm.According to the band gap(eV) formula,the band gap value is calculated to be 0.657 8 eV.The extreme electrical-to-optical conversion efficiency achieved was about 15%.By the first principles,we analysed the reason of the changing of the band gap value,and then compared the result with previous one.The internal structure of mineral is the important factor affecting the photoelectric conversion.The light absorption characteristics of FeS2-Fe1-xS heterostructures synthesized under hydrothermal conditions is better than the characteristics from natural pyrite with defects of Co and Ni.The heterostructures can improve the electrical-to-optical conversion efficiency and provide scientific basis for the absorption characteristics research of Fe-S series materials.