The invention discloses a preparation method of a 6-phosphoryl substituted phenanthridine derivative, and belongs to the technical field of organic synthesis. The method comprises the steps that biphenyl isothiocyanate and diaryl oxygen and phosphorus are added into a reactor, by being catalyzed by manganese, heating is conducted in a solvent, after a reaction is completed, cooling is conducted to reach room temperature, a system is diluted with ethyl acetate and washed with saturated sodium chloride, an organic phase is combined, a filtrate is concentrated through a rotary evaporator, a coarse product is obtained, and finally a product is obtained through column chromatography separation. The synthetic method is easy to implement, raw materials are easy to prepare, multiple substituent groups are introduced simultaneously, the product is easy to purify and separate, the yield is high, and the method is suitable for synthesizing the 6-phosphoryl substituted phenanthridine derivative. The reaction equation of the derivative is defined in the description.