The title compound, 2-(3-silatranylpropylamino)-4-dichlorophenyl-5,5-dimethyl-1,3,2-dioxaphosphorinane-2-oxide(2(C_(20)H_(33)N_2O_6Psi)·C_2H_6O·CH_4O, Mr = 991.20), has been synthesized by the nucleophilic substitution reaction of 2-chloro-4-phenyl-5,5-dimethyl-1,3,2-dioxaphosphorinane-2-oxide with γ-aminopropylsilatrane, and its crystal structure was determined by single-crystal X-ray diffraction. The crystal belongs to the triclinic system, space group P1 with a = 10.3783(15), b = 11.2402(17), c = 12.1675(18) ?, a = 70.653(4), b = 82.908(4), g = 85.690(4)°, V = 1328.1(3) ?3, Z = 1, Dc = 1.239 g/cm~3, μ = 0.19 mm~(-1), F(000) = 532, the final R = 0.0640 and wR = 0.2090 for 3615 observed reflections with I > 2s(I). The cyclic dioxaphosphorinane ring in the molecule adopts a thermodynamically stable cis conformation, while the silatrane fragment forms a cage-like structure in which there exists an intramolecular Si?N donor-acceptor bond. In the crystal structure, centrosymmetrically related molecules are linked by pairs of N–H···O hydrogen bonds into dimers, generating rings with graph-set motif R22(8). Furthermore, a couple of O(7)–H(10)···O(3) hydrogen bonds were formed by O atom of P=O and H atom from hydroxyl in the solvent ethanol. Thermal property of the compound was also studied by means of thermogravimetry(TGA). The thermal analysis and preliminary fireproofing test show that the title compound has good flame retardance. The title compound, 2- (3-silatranylpropylamino) -4-dichlorophenyl-5,5-dimethyl-1,3,2- dioxaphosphorinane-2-oxide (C20H33N206Psi) · C_2H_6O · CH_4O , Mr = 991.20), has been synthesized by the nucleophilic substitution reaction of 2-chloro-4-phenyl-5,5-dimethyl-1,3,2- dioxaphosphorinane-2-oxide with γ-aminopropylsilatrane, and its crystal structure was The crystal belongs to the triclinic system, space group P1 with a = 10.3783 (15), b = 11.2402 (17), c = 12.1675 (18) ?, a = 70.653 (4) , b = 82.908 (4), g = 85.690 (4) °, V = 1328.1 (3) 3 3, Z = 1, Dc = 1.239 g / cm 3, μ = 0.19 mm -1, F 000) = 532, the final R = 0.0640 and wR = 0.2090 for 3615 observed reflections with I> 2s (I). The cyclic dioxaphosphorinane ring in the molecule adopts a thermodynamically stable cis conformation, while the silatrane fragment forms a cage-like structure in which there exists an intramolecular Si? N donor-acceptor bond. In the crystal structure, centrosymmetricall y related molecules are linked by pairs of N-H ··· O hydrogen bonds into dimers, generating rings with graph-set motif R22 (8). Further, a couple of O (7) -H (3) hydrogen bonds were formed by O atom of P = O and H atom from hydroxyl in the solvent ethanol. Thermal property of the compound was also studied by means of thermogravimetry (TGA). The thermal analysis and preliminary fireproofing test show that the title compound has good flame retardance.