Two novel substituted phenyl isoxazole benzoxazine formamide derivatives were designed and synthesized with substituted o-aminophenol, 1,2-dibromoethane and different phenyl substituted isoxazole formyl chloride as the raw materials via microwave assistant synthesis. The target compounds were characterized by IR, ¹H NMR, ¹³C NMR and HRMS. Both single-crystal structures were further determined by X-ray diffraction. 3-(2΄-Chloro-6΄-fluoro-phenyl)-4-(2΄,3΄-dihydro-1΄,4΄-benzoxazine)-5-methyl-isoxazole formamide (4a) crystallizes in orthorhombic system, P2₁ space group with a = 8.9414(18), b = 10.834(2), c = 17.706(4) Å, V = 1715.1(6) ų, D_c = 1.444 Mg/m³, Z = 4, F(000) = 768, m(MoKa) = 0.255 mm^-1, R = 0.0406 and wR = 0.1171. 3-Phenyl-4-(6- methyl-2΄,3΄-dihydro-1΄,4΄-benzoxazine)-5-methyl-isoxazole formamide (4b) is of triclinic system, space group P  with a = 7.7659(16), b = 8.3626(17), c = 13.484(3) Å, a = 76.04(3)°, b = 100.63(3)°, g = 82.01(3)°, V = 841.6(3) ų, D_c = 1.319 Mg/m³, Z = 2, F(000) = 352, m(MoKa) = 0.090 mm^-1, R = 0.0672 and wR = 0.2671. Both crystals are packed through C–H···O hydrogen bonding interaction. There is C–H···F hydrogen bond between 4a molecules, and C–H···N between 4b molecules. Bioassay results showed that compounds 4a and 4b exhibited detoxification on maize and restored maize growth index.