The invention discloses a hexahydroxy nitride oxide silicon heterocyclic compound and a preparation method thereof. The compound is shown as a formula (I); R1 is straight chain C1-C6 alkyls, C1-C5 alkyls with side chains or halogen-containing groups; R2 is straight chain C1-C5 alkyls, C1-C4 alkyls with side chains or substitutional straight chains or branched chain alkyls or halogen groups; Ar isC6-C10 aromatic groups or substitutional aromatic groups. The compound can be used as amidogen containing silicone oil and silicone rubber; preparation monomers of the heterocyclic compound with photoelectric performance have good application prospects. The invention also further discloses a method for preparing the heterocyclic compound in a formula (I) from a silane reduction Schiff base compound under the condition without catalysts. The reaction conditions are mild; the reaction time is short (smaller than 2h); the yield reaches 90 percent or above; the silane and imine reaction is enriched; a shortcut is provided for preparing the nitride oxide silicon heterocyclic compound through one-step method intramolecular cyclization reaction. (The formula (I) is shown in description.).