Abstract: Objective To observe calf thymus DNA damage induced by potassium dichromate in combination with glutathione (GSH). Methods Atomic force microscope and ultraviolet spectrum (UV) were used to observe the alterations of the DNA ultrastructure and absorption spectrum. Results Atomirc force microscopy revealed no breaks of the DNA strand in response to treatment with potassium dichromate alone, but when coupled with GSH at proper concentrations, potassium dichromate induced alterations in the DNA structure and DNA fragmentation. UV examination also confirmed these findings by showing increased absorption intensity of the maximum UV peak following combined treatment of the DNA with potassium dichromate and GSH. Conclusion These morphological and spectrographic evidences verified the important role of GSH in mediating the generation of various tumor-inducing intermediate products of potassium dichromate.