The invention discloses a semi-synthesis method of phenolic hydroxyl 
flavonoid compounds and an 
iodine recycling method, relating to two ways A and B and 
iodine recycling, wherein in the way A, flavone is easily dissolved in a 
pyridine solvent of 
ethylene glycol or glycerin, and with 
iodine as a dehydrogenating agent, flavone is generated by heating and 
dehydration; in the way B, 
flavanone or flavone is not dissolved in 
pyridine of 
alcohol, the complexing of trivalent aluminum and 
flavanone is adopted, the 
solubility of the complexing and 
dehydrogenation products is high in 
alcohol, flavone is separated from the 
aluminum complex by use of 
phosphoric acid and the like, and flavone insoluble in water is separated out and obtained by filtering. The method disclosed by the invention is a universal method for preparing 
flavonoid compounds through 
dehydrogenation of phenolic hydroxyl dihydro flavonoids, the dosage of the reagents such as 
pyridine and the like is very small, and the treatment is simple, so that the method is suitable for industrial production. Take the 
diosmin preparation using 
hesperidin as an example, compared with the existing documents and patents, in the method disclosed by the invention, the dosage of organic solvents such as pyridine and the like is the least, the treatment is the simplest, the yield is the highest, and the method is environment-friendly (iodides can be oxidized by 
hydrogen peroxide, the recycling process is simple, and the yield is relatively high), and industrial production is easy to realize.