Two 5-pyrimidinyl-1,2,4-oxadiazoles were synthesized through two different routes and their structures were characterized by single-crystal X-ray diffraction, NMR and MS. Compound 3, 5-(2-chloro-4-methyl-6-phenylpyrimidin-5-yl)-3-phenyl-1,2,4-oxadiazole, crystallizes in orthorhombic, space group Pbca with a = 19.1575(11), b = 8.2115(5), c = 21.2035(12), V = 3335.6(3)3 and Z = 4. Compound 6, 5-(2,6-dichloropyrimidin-4-yl)-3-phenyl-1,2,4-oxadiazole, crystallizes in monoclinic space group Pn with a = 8.4275(13), b = 5.4088(8), c = 13.493(2), β = 99.768(3)o, V = 4658.6(6)3 and Z = 8. Preliminary bioassay indicated that the two title compounds had good herbicidal activities. Two 5-pyrimidinyl-1,2,4-oxadiazoles were synthesized through two different routes and their structures were characterized by single-crystal X-ray diffraction, NMR and MS. Compound 3, 5- Crystallization in orthorhombic, space group Pbca with a = 19.1575 (11), b = 8.2115 (5), c = 21.2035 (12)  6-phenylpyrimidin-5-yl) , V = 3335.6 (3) 3 and Z = 4. Compound 6, 5- (2,6-dichloropyrimidin-4-yl) -3-phenyl- 1,2,4- oxadiazole, crystallizes in monoclinic space group Pn with a = 8.4275 (13), b = 5.4088 (8), c = 13.493 (2) , β = 99.768 (3) o, V = 4658.6 (6) 3 and Z = 8. Preliminary bioassay indicated that the two title compounds had good herbicidal activities.