An electrochromic medium comprises a 
cathode electrochromic compound, wherein the 
structural formula of the 
cathode electrochromic compound is as shown in the specification, R1 is selected from normal 
alkyl or heterogeneous 
alkyl containing 1-20 carbon atoms; each of R2-R14 is independently selected from H, 
alkyl, cycloalkyl, polycyclic alkyl, 
aryl, heterocyclic alkyl, aromatic alkyl and alkaryl containing 1-50 carbon atoms or alkyl, cycloalkyl, polycyclic alkyl, 
aryl, heterocyclic alkyl, aromatic alkyl and alkaryl containing 1-50 carbon atoms and 
halogen, N, O, S, Si, P or unsaturated bond groups; X1<-> is selected from acetate anion, methyl 
phenyl acetate sulfonate anion, 
tetrafluoroborate anion, hexafluoroborate anion, tetraphenyl borate anion, trifluoro 
mesylate anion, 
perchlorate anion, bis-
oxalate borate anion, 
oxalate difluoroborate anion, bis(trifluoromesyl) 
imide anion and tri(trifluoromesyl) methyl anion. The 
cathode electrochromic compound has the advantages that good electrochemical reversibility is achieved, fast color changing and good stability are achieved, the lowest value of visible light 
transmittance is small, and the like.