The title compound 2-morpholinylthioformyl-2-phenyl-4-mor-pholinyl-5- phenyl-1, 3-dithiole (C24H26N2O2S3 Mr = 470.66 ) was obtained by the re-action of α-thiobenzoylthioformmorpholine (1) with trimethyl phosphite. The crystal is monoclinic, space group P21/n, with unit cell parameters: a = 9. 746(2), b = 21. 124(8), c=11.484(3) (A。), β=99.98(2)°, Z=4, V=2328(1)(A。)3, Dc=1.343g/cm3,μ(MoKα)=3.42 cm-1, F(000)=992.00. R=0.054, Rw =0.062 for 2426 observed reflections (Ⅰ＞ 2.00σ (Ⅰ)). X-ray analysis reveals that interatomic distance for C(1)-C(2) is 1.338(5) (A。), indicating that it is a double bond. The atoms C(1),C(2), C(3), S(1) and S(2) form a 1, 3-dithiole ring, in which S(1), C(1), C(2) and S(2) are coplanar. The X-ray results support our proposed mechanism for the reaction.