The invention discloses a phosphoric organic silicon compound, a preparation method and application thereof. The structural formula of the phosphoric organic silicon compound is shown as Figure 1, wherein, R1, R2, R3 and R4 are selected from C1-C5 alkyl, C1-C5 alkoxy, aryl, aryl substituted by halogen and aroxy; R5 and R6 are C0-C5 alkylidene groups; R7-R14 are selected from hydrogen atom, C1-C5 alkyl, nitro, the C1-C5 alkoxy, aryl, the aryl substituted by the halogen and the aroxy; and n is 1-10. The preparation method comprises performing an addition reaction of an active phosphorus-hydrogen bond in a 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide (DOPO) derivative and siloxane containing two carbon-carbon double bonds to produce the novel phosphoric organic silicon compound. The compound contains two elements namely phosphorus and silicon which have flame retardant property, and can be taken as an additive flame retardant for inflaming retarding of high molecular materials.